Objective To assess the clinical efficacy of modified endoscopic mucosal resection (M- EMR )treatment for flat colorectal polyps. Methods A total of 276 aged patients with flat colorectal polyps were divided into two groups randomly:EMR groups with 136 aged patients 152 lesions. M-EMR groups with 140 aged patients 145 lesions. After submucosal injection of physiological saline, EMR groups: enbloc resection were performed. M- EMR groups:cut open mucosa around the lesions before resection with snare pointed end. All resected specimens were retrieved for pathologic study. compare the rate of complication, the time of operation,the rate of enbloc resection and the rate of recurrence in the two groups.Results All polyps were removed completely. EMR groups: 1 delayed bleeding,1 perforation,1 postpolypectomy syndrome, the rate of complication was 2.0%(3/152). M-EMR groups : 1 delayed bleeding,1 postpolypectomy syndrome, the rate of complication was 1.4%(2/145) .The time of operation were(5.6±2.0)min in EMR groups, (5.7±2.1)min in M-EMR groups,there was no significant difference between two groups(p>0.05). The rate of enbloc resection was 92.1%(40/152)in EMR groups,The rate of enbloc resection was 100%(145/145)in M-EMR groups, there was statistic significance(p<0.05). Postoperative pathological examination showed 135 tubular adenomas, 40 villous adenomas, 57 tubular villous adenomas, 29 hyperplastic polyps, 34 inflammatory polys. 8 adenoma with high-grade intraepithelial neoplasia, 1 lesion was removed incompletely in EMR groups, resection of the involved intestinal segment was made,all showed no recurrence in 6 months. 2 mucosal carcinoma in M-EMR groups were removed completely , showed no recurrence in 6 months . 12 lesion was removed incompletely in EMR groups,1 operation,11 APC was made, showed 1 recurrence in 6 months ,the rate of recurrence was 0.66%(1／152),no recurrence in M-EMR groups. Conclusion M- EMR appears to be an efficacious procedure to treat flat colorectal polyps than EMR.