Inclusion Criteria:  ① ALS patients in outpatient or ward voluntarily participated in the study and signed informed consent by themselves or their authorized family members; ② At the time of enrollment, the diagnostic grade of ALS patients met the criteria of the World Federation of Neurology (WFN) revised in 1998; ③ They were 18-75 years old; ④ Antibiotics, L-carnitine and intestinal flora regulation were not used within 3 months; ⑤ Can eat normally.  Exclusion Criteria:  ① electromyography detection found motor nerve block, sensory nerve conduction abnormalities, or imaging examination (CT or MRI) found lesions that could explain the clinical manifestations of patients, which did not support the diagnosis of ALS; ② The patients with dementia or mental disorder could not cooperate with the researchers; ③ Patients with severe heart, liver, kidney and other severe concomitant diseases; ④ Patients with gastrointestinal diseases or gastrointestinal surgery may affect gastrointestinal absorption; ⑤ The patients who were treated with antibiotics, L-carnitine and intestinal flora regulation in recent 3 months; ⑥ Breast feeding or pregnancy; ⑦ Patients with dysphagia, inability to eat normal food, or indwelling gastric tube or gastrostomy for enteral nutrition.