Objective To evaluate the safety and efficacy of self-expanding metallic stents (SEMS) in one-stage surgery for patients with left-sided malignant colorectal obstruction. Methods The clinical data of 97 patients with left-sided colorectal cancer who had been admitted to the First Affiliated Hospital of Zhejiang Chinese Medical University from May 2005 to September 2008 were retrospectively analyzed. Forty-six patients with left-sided malignant colorectal obstruction were in the test group, after the placement of SEMS, they received one-stage resection and anastomosis; 51 patients with left-sided colorectal cancer (without obstruction) were in the control group, and they received one-stage surgery. The defecation and anal exhaust time, hospital stay and incidence of postoperative complications between the 2 groups were analyzed. All data were analyzed via t test or chi-square test. Results One patient in test group had acute diffuse peritonitis which was induced by intestinal perforation at postoperative day 4, and was treated with radical resection for sigmoid cancer. One-stage surgery was successfully performed on 45 patients, and they were discharged at postoperative day 11-16. One patient died of respiratory infection and heart failure at postoperative day 10. All patients were followed up for 4-48 months. There was no significant difference in defecation and anal exhaust time, hospital stay, incidence of perioperative complications, recurrence, metastasis and survival within follow-up interval between the 2 groups (t=0.164, 1.358, χ~2 = 0.252, 1.200, 0.580, P >0.05). Conclusion SEMS is effective and safe in the treatment of left-sided malignant colorectal obstruction.