Inclusion Criteria:  Patients with moderate and severe ulcerative colitis; Subjects were above 18 years old and below 80 years; Indications of 5-ASA or biological treatment; According to the clinical symptoms, ulcerative colitis was diagnosed by endoscopic changes, pathological manifestations. The disease activity of UC was assessed according to the modified Mayo scoring system (modified Mayo: 6~12 for patients with moderate to severe ulcerative colitis); If the subject is a woman, a pregnancy test at baseline is needed to exclude pregnancy. Female patients must follow the contraceptive recommendations of the project; Subjects must be able and willing to provide written informed consent and comply with the requirements of this study protocol.  Exclusion Criteria:  No indications of 5-ASA or biological treatment; ulcerative colitis patients who had previously undergone a partial colectomy; Patients who are unable to use 5-ASA for a long time; Patients with severe, progressive, or uncontrolled kidney, liver, blood, or endocrine diseases or symptoms; Presence of infected persons, Patients with a contraindication to the use of biological agents such as C. difficile infection or other intestinal pathogens, active tuberculosis or intestinal tuberculosis infection, human immunodeficiency virus (HIV) infection, active hepatitis B or hepatitis C (defined as: ① HBV: hepatitis B surface antigen (HBs Ag) positive (+), Or patients with positive for hepatitis B core antibody (HBcAb) and the qualitative test results of HBV deoxyribonucleic acid (DNA) polymerase chain reaction (PCR) meet the detection criteria; ② HCV: Any patient with an anti-HCV antibody (HCV Ab) -positive patient with a detectable HCV ribonucleic acid (RNA); Patients with a history of gastrointestinal dysplasia, or dysplasia on any biopsy performed on endoscopy, excluding low-grade dysplasia lesions; known history of lymphoproliferative disease (including lymphoma), or signs and symptoms (e. g., lymphadenopathy and / or splenomegaly); patients with current or previous malignancy; Has been involved in other clinical studies.