Objective To compare the short-term and long-term effects of emergency surgery (ES) and self-expanding metal stent (SEMS) for treatment of malignant left-sided colonic obstruction.Methods The patients with malignant left-sided colonic obstruction who met the inclusion and exclusion criteria in the Third Affiliated Hospital of Soochow University from October 2010 to October 2020 were retrospectively collected and divided into an ES group (n=43) and a SEMS group (n=22). The baseline data, surgical data, postoperative data, and prognosis (overall survival and relapse free survival) were compared, and the risk factors of tumor recurrence after surgery were further analyzed.Results In this study, 65 cases of malignant left-sided colonic obstruction were included, including 43 cases in the ES group and 22 cases in the SEMS group. There were no statistical differences in the baseline data of the two groups (P>0.05). There were no significant differences in the incidence of postoperative complications ［13.6% (3/22) vs. 23.3% (10/43), P=0.555］, recurrence rate ［40.9% (9/22) vs. 37.2% (16/43), P=0.772］, and the rate of receiving postoperative chemotherapy ［68.2% (15/22) vs. 48.8% (21/43), P=0.138］ between the SEMS group and ES group. Compared with the ES group, although the median hospitalization time was longer (20 d vs. 12 d, P=0.001), and the median hospitalization cost was higher (65 033 yuan vs. 40 045 yuan, P=0.001), the stoma rate of the SEMs group was lower ［36.4% (8/22) vs. 88.4% (38/43), P=0.001］, and the minimally invasive (laparoscopic) rate was higher ［36.4% (8/22) vs. 7.0% (3/43), P=0.008］. There were no significant differences in the 4-year cumulative overall survival (46.9% vs. 48.4%, P=0.333) and 4-year cumulative relapse free survival (36.2% vs. 44.8%, P=0.724) between the SEMS group and ES group, but the overall survival of SEMS group was better than that of the ES group for the patients with stage Ⅲ–Ⅳ (χ2=4.644, P=0.047). Cox proportional hazards regression mode multivariate analysis showed that the TNM stage was the independent risk factor for the postoperative recurrence of patients with malignant left-sided colonic obstruction ［HR=1.753, 95%CI (1.081, 2.842), P=0.023］. Conclusions Short-term and long-term effects of ES and SEMS for treatment of malignant left-sided colonic obstruction are equivalent. Although SEMS mode has a longer hospital stay and higher hospitalization costs, stoma rate is lower and laparoscopic surgery rate is higher. Overall survival of SEMS mode for treatment malignant left-sided colonic obstruction patients with stage Ⅲ–Ⅳ is better.