Objective To evaluate the effect of postmastectomy radiotherapy(PMRT)on the rate of loco-regional recurrence and survival for breast cancer patients undergoing radical mastectomy with one to three positive lymph nodes. Methods The database of Pubmed, Embase, EBM Reviews-Cochrane Central Register of Controlled Trials, CBM, CNKI, VIP, and Chinese Cancer were searched. All randomized controlled trials about postmastectomy radiotherapy on breast cancer patients with 1-3 positive lymph nodes were considered for inclusion. Revman 5.3 was used in the meta analysis. Results Four trials enrolled 1 254 breast cancer women with 1-3 positive lymph nodes were included. The studies were high quality according to the evaluations of the quality criteria. After 10 to 20 years follow-up, the results showed that, 460 patients were analyzed in the result of loco-regional recurrence, the hazard ratio (HR) was 0.23, 95%CI (0.15, 0.37), the result showed statistical difference (P＜0.000 01), and the heterogeneity was existed (P=0.09,I2=59%). One thousand two hundred and fifty-four patients were analyzed in the result of overall survival, theHR was 0.82, 95%CI (0.71, 0.93), the result showed statistical difference (P=0.002 ), and there did not existed heterogeneity (P=0.65,I2=0%). Four hundred and sixty patients were analyzed in the result of metastasis-free survival, theHR was 0.71, 95%CI (0.56, 0.90), the result showed statistical difference (P=0.005), and there did not existed heterogeneity (P=0.63,I2=0%). Nine hundred and seventy-seven patients were analyzed in the result of disease free survival, theHR was 0.74, 95%CI (0.66, 0.85), the result showed statistical difference (P＜0.000 01), and there did not existed heterogeneity (P=0.49,I2=0%). Conclusion Through this systematic review, we consider that postmastectomy radiotherapy could reduce the loco-regional recurrence and increase the overall survival for long-term.