Some studies have shown that rifaximin is effective in the management of Crohn's Disease. Meanwhile, its adverse effect is tolerable. But no study has been conducted to assess its effect on preventing postoperative recurrence. Thus, we conduct a randomised controlled study to assess the effect of rifaximin combined with thiopurine on preventing postoperative endoscopic recurrence in Crohn's disease, compared with thiopurine. The primary endpoint is the rate of endoscopic recurrence at 6 months.