for some patients with Crohn's diseases undergoing surgery，whether exclusive enteral nutrition(EEN) could delay the disease relapse needs exploration.The trial will study whether the efficacy of postoperative EEN could help keeping remission.

For patients with Crohn's disease(CD), whether exclusive enteral nutrition(EEN) following bowel resection and anastomosis could delay the disease recurrence remains unkown. In this study， CD patients after surgery will be divided into two groups: one group is treated with 3 months' EEN and then turn to normal diet after 3 months; the other group is given with normal diet all through. All patients will be adminstrated with oral azathioprine after surgery. Then, the rates of 1 year postoperative endoscopic recurrence will be compared between groups.

Inclusion Criteria:

• CD patients who undergoing bowel resection with anastomosis

Exclusion Criteria:

• patients who had administered with immunomodulators or biological agents patients who were created stoma