Crohn's disease (CD) is a chronic recurrent intestinal inflammation involving the whole digestive tract, with high disability rate, high surgical rate and high recurrent rate postoperatively. Preventing postoperative recurrence in CD patients is an important clinical problem needed urgent intervention. Azathioprine (AZA) and infliximab (IFX) effectively prevent postoperative recurrence in CD patients, but the postoperative recurrence rate is still as high as 41%. Oral supplement of n-3 polyunsaturated fatty acids (n-3 PUFA) owns the advantages of high compliance and low economic cost. We aim to evaluate the effect of routine treatment (AZA/IFX) combined with long-term dietary n-3PUFA on the prevention and treatment of postoperative recurrence of CD, which help optimize the treatment strategy for the prevention of postoperative recurrence.