The human gut microbiome is one of the most densely populated microbial communities on Earth and contains highly diverse microbial communities that provide metabolic, immune and protective functions and play a critical role in human health. The gastrointestinal microbiota is influenced by a variety of factors, including neurological stress, genetics, host physiology (host age, disease, etc.), and environmental factors such as living conditions and drug use. At the same time, the vagus nerve (VN) is considered a key component of the autonomic nervous system (ANS), which innervates most of the digestive tract and many gastrointestinal organs such as the esophagus, stomach, small intestine, and colon, as well as vital organs such as the liver, pancreas, and gallbladder in the digestive system. The vagus nerve transmits excitement to the corresponding brain region by sensing intestinal stimulation, and regulates the gut and brain bidirectionally through the "gut-brain axis". Recent studies have shown that VN has anti-inflammatory effects. This vagus function is mediated through a variety of pathways, some of which remain controversial. The first is the anti-inflammatory pathway of the hypothalamic-pituitary-adrenal axis, stimulated by the afferent fibers of the vagus nerve, where the adrenal glands release cortisol, which provides an important first innate defense against inflammatory infections and helps restore homeostasis in the body. The second, known as the cholinergic anti-inflammatory pathway, releases acetylcholine (ACh) at the synaptic junction with macrophages through the vagal efferent fibre-mediated synaptic connections of intestinal neurons. Acetylcholine binds to the α-7-nicotinic acetylcholine receptor of macrophages and inhibits the release of tumor necrosis (TNF)α, a pro-inflammatory cytokine. The final pathway is the splenic sympathetic anti-inflammatory pathway, where VN stimulates the splenic sympathetic nerve to release acetylcholine from norepinephrine (norepinephrine) at the distal end. Finally, ACh inhibits the release of TNF-α from splenic macrophages through the α-7-nicotinic ACh receptor. Irritable bowel syndrome (IBS) is a very common functional digestive disorder characterized by chronic abdominal pain and altered bowel habits in the absence of biological or structural abnormalities. In the field of IBS, effective drug treatments are very limited, and patients are urgently looking for alternatives, including probiotics, hypnotherapy, osteopathy, dietary changes, and fecal microbiota transplants. In recent years, with the continuous elucidation of vagus nerve mechanisms, IBS patients are increasingly interested in bioelectrical regulation, and these patients are often skeptical of traditional drug treatment and believe that drugs are prone to side effects. For several reasons, vagus nerve stimulation (VNS) may be a promising option for improving IBS symptoms. Vagus nerve stimulation (VNS) is currently used as a treatment option for many clinical conditions, such as heart failure, migraines, and inflammatory bowel disease. VNS techniques are mainly divided into invasive (surgical implantation) and non-invasive (percutaneous)VNS techniques. Invasive VNS (iVNS) involve implanting a programmable pulse generator device in the chest wall and placing electrodes around the left (typical) cervical vagus nerve. As it stands, iVNS has several potential risks, such as bradycardia and cardiac arrest, and localized infections around the wound. The transcutaneous VNS (tVNS) delivery system relies on the skin distribution of the afferent nerve of the vagus nerve to intervene in the outer ear (the auricular branch of the vagus nerve) or the neck (the cervical branch of the vagus nerve), thereby avoiding the risk of surgical implantation of the VNS delivery device and promoting further research on the application of tVNS. In this experiment, the portable ear nail stimulator produced by Ruishen Medical can accurately stimulate the ear nail, transdermal stimulation of the ear vagus nerve, and give full play to its therapeutic effect. Therefore, the purpose of this clinical trial is to use ear nail stimulator in patients with IBS to explore whether it has therapeutic effects on patients with IBS. To explore the influence of tVNS therapy on irritable bowel syndrome compared with drug therapy, it is hoped that the use of TVNS therapy can reduce the use of related drugs, or even replace drugs. This study intends to recruit a group of patients with IBS to use the portable ear nail stimulator. The purpose of the study is (1) to observe whether the symptoms of IBS patients are improved; (2) To analyze the changes of intestinal microbes in patients with IBS; (3) Verify whether the level of intestinal inflammation is reduced and discover metabolic markers in the intestine. This was a randomized, double-blind study with no placebo group and enrolled 40 patients diagnosed with diarrheal irritable bowel syndrome. The enrolled patients were randomly assigned to tVNS true stimulation (real transcutaneous vagal stimulation) and false stimulation (same instrument but no vagal stimulation) at different times. This study does not require recruitment advertisements, and subjects are recruited on a completely voluntary basis. Possible risks during the experiment are explained to subjects and informed consent is signed after they agree to join the study. The volunteers who agreed to join the experiment were surveyed by questionnaire to obtain their intestinal health and other health conditions, and screened according to the above research object selection criteria and exclusion criteria. The collected samples are named by number, which will not disclose the personal information of the subjects. The identity of the subjects is kept secret throughout the study process, and only the number and disease phenotype are visible. Subjects may withdraw from the study at any time. This study will analyze the composition and structure of the gut microbiota of the subjects, and the subjects can keep abreast of the progress of the testing and analysis and obtain their own relevant data. In this study, the Ruishenan auricular vagus nerve stimulator is used directly without installation. Easy to carry, can be opened at any time stimulation, does not affect daily work and life. Currently approved indications are: adjuvant therapy for sleep disorders, anxiety, loss of appetite, fatigue, and adjuvant therapy for diabetes. In this study, ear nail stimulation with a pulse width of 200μs and a frequency of 30Hz was used for 3 hours a day for 8 weeks to improve the clinical symptoms of patients with irritable bowel syndrome. The experimental plan was to collect stool samples from the recruited patients with diarrheal irritable bowel syndrome, and use the ear conchal stimulator for 3h every day with pulse width of 200μs and frequency of 30Hz. The treatment lasted for 8 weeks \[28\], and each patient was randomly selected as true or false stimulus every 4 weeks, and a total of 4 groups were generated, namely true-true, true-false, false-true, and false-false (Figure 2). The volunteers' stool samples were collected on days 0, 28 and 56. Stool samples were collected two weeks after treatment. On day 0 and every 7 days thereafter, the patients filled in the questionnaire, and a total of 11 questionnaires were collected.