Objective To explore influencing factors for complete resection and operation time of endoscopic submucosal dissection（ESD） for colorectal tumors. Methods This retrospective study included 95 consecutive colorectal tumors in 88 patients whose pathological diagnosis was adenoma and carcinoma， treated with ESD at the Department of Endoscopy of the First Hospital of Jilin University from January 2013 to December 2014. Multiple logistic regression analysis was conducted on the factors related to complete resection and operation time. Results Average tumor size was 28.7±14.1 mm（range，8-80 mm）， and the average procedure time was 80.72±63.90 min. The rate of complete resection was 92.6％（88／95），and the rate of incomplete resection was 7.4％（7／95）. Multivariate logistic regression analysis revealed that fibrosis （P=0.012，OR=52.473， 95％CI：2.571-1 140.438） contributed to incomplete resection. Fibrosis （P=0.001，OR=0.045， 95％CI：0.007-0.289），tumor size （P=0.035，OR=0.170， 95％CI：0.033-0.884），granular-type laterally spreading tumor（P=0.013，OR=34.432， 95％CI：2.138-554.476）， non-granular-type laterally spreading tumor（P=0.044，OR=31.715， 95％CI：1.093-919.904） were independent factors for extending operation time of colorectal ESD. Conclusion The severer fibrosis can induce higher rate of incomplete resection. The more severe fibrosis is， the larger tumor size is， and the longer operation time is.