To indicate the efficacy of Fecal microbiota transplantation (FMT) for the treatment of Ulcerative colitis (UC), The investigators design a multicenter, randomized controlled trial to perform FMT through colonic transendoscopic enteral tubing (TET) way, and evaluate the efficacy and safety of FMT for patients with moderate or severe UC.

1. Patients with moderate to severe UC will be screened (Mayo>6）.
2. Participants will be divided into control and study groups by double blind.
3. Control group and study group will receive a colonic endoscopy evaluation. And a TET tube will be fixed at ileocecum.
4. Enema with 5-ASA 4g/day for 7days by TET will be performed as basic therapy for both control and study group. Study and control group will be given with fecal microbiota suspension and equal volume of saline by TET for three times every other day in one week.
5. The follow-up will be performed at 1 week, 4 weeks and 12 weeks after first treatment. All the participants will receive a endoscopy evaluation at 12 weeks. Clinical remission, clinical improvement and safety are the primary endpoint at 12 weeks; Intestinal microbiota changing is recognized as the secondary endpoint.

Inclusion Criteria:

• Active, moderate to severe severity (Mayo score more than 6)
• Safety using history of 5-ASA.
• Able to undergo endoscopy examination.

Exclusion Criteria:

• Immunosuppressive drugs and glucocorticoids using in 4 weeks
• Antibiotic using in 7 days
• High risk of toxic megacolon
• Colon cancer or neoplasia in pathophysiology
• Other severe diseases (eg: cardiovascular, respiratory, gastroenteral and kidney diseases)