Abstract: Objective To evaluate the CT finding and diagnosis of postoperative recurrence of rectal carcinoma. Methods 49 postoperative rectal cancer patients were preformed CT scans of 64 times. Results CT scan indicated that cancer relapsed 3 to 84 months after surgery.For patients with colostomy,the CT scan showed nodular or lobulated mass in the areas of perineum and presacralis,as well as loss of presacral fat space.For patients without colostomy.CT finding included thickened rectal wall with unregular proximal tumor,rectal obliteration,rectostenosis and ddisplacement of perirectal fat space. Conclusion For judgring whether cancer relapsed and the postoperative changes on CT film,it was necessary to have information ablut the approach of surgery.Our study suggested it was difficult to differentiate tumor recurrence from fibrosis causeed by surgery of rediotherapy ad granulation tissue.And for some cases,needle biopsy was required.