There are many limitations in the current treatments of Inflammatory bowel disease (IBD). Now the investigators realized that the intestinal microecological is closely associated with the development of IBD. So the standardized fecal microbiota transplantation is considered to be simple but effective emerging therapies for the treatment of IBD. In this project the investigators intend to carry out a single-center, randomized, single-blind clinical intervention study. The investigators will recruit 40 patients with IBD (20 cases of Ulcerative Colitis and 20 cases of Crohn's disease) in China. The patients will be randomly divided into 2 groups, one group will be given treatment of standardized fecal microbiota transplantation, the other will be simply treated with mesalazine, followed up for at least 1 year. The investigators propose to determine the efficiency, durability and safety of Standardized Fecal Microbiota Transplantation for IBD treatment.

In this projects the investigators aim to re-establish a gut balance of intestinal microecological through Standardized Fecal Microbiota Transplantation for IBD (UC and CD). We will establish a standardized isolation, store, and transportion steps of fecal bacteria from donated fresh stool in the laboratory. Then the bacteria will be transplanted to mid-gut by nose-jejunum nutrition tube. Patients in this study will be assigned to receive standardized FMT only once or traditional medicine of mesalazine and would be followed up for at least 1 year. The clinical symptoms, sign, blood tests, abdominal CT, endoscopy and questionnaire will be used to assess the efficiency, durability and safety of Standardized FMT at the start and end of the projects.

Inclusion Criteria:

• Severe IBD define as HBI score ≥ 9.
• Moderate IBD define as 7<HBI <9
• Montreal classification: Age > 14 years old, Location L1-3, Behavior B1-3.

Exclusion Criteria:

• Diarrhea activity scores < 3
• Severely active disease with perianal diseases
• Severely active disease with indication of surgery.
• Diagnosis as IBD first time or first year.
• No history of using 5-ASA, biological (antibody), immunomodulatory therapy, corticosteroid therapy