Objective To investigate the risk factors of operation time of endoscopic submucosal dissection (ESD) for superficial gastric lesions. Methods Clinicopathologic data of 193 patients(195 lesions) diagnosed with early gastric cancer preoperatively and undergone ESD in Beijing Friendship Hospital from January 2015 to December 2017 was retrospectively collected, including basic information (age, gender, BMI, comorbidities), lesion characteristics (size, location, morphology), operation time (anesthesia time), the operators’ experience of ESD and postoperative pathology, etc. Univariate analysis was performed to find the risk factors of ESD operation time, and logistic regression analysis was performed on the factors with statistical differences in univariate analysis to find the independent risk factors with ESD operation time over 120 min. Results The mean age of the patients was 63.34±9.11 years. The median time of ESD operation was 120.00 (95.00,165.00) min and the median size of the lesion was 1.50 (1.00, 2.38) cm. Early gastric cancers were diagnosed in 164 lesions (84.10%), among which 162 lesions (98.78%) achieved En bloc resection, and 148 lesions (90.24%) achieved curative resection. The gender(P=0.018), location（P＜0.001）and size(r=0.209，P=0.007) were considered influential factors on the operation time by univariate analysis, while age, body mass index, American Society of Anesthesiologists grade (ASA), roughness of lesion surface, presence or absence of white moss and ulcer, depth of lesion invasion, operative period, gross shape of lesion, degree of differentiation and experience of operator were not associated with operation time(P >0.05). Multivariate analysis showed that the lesion located in the cardia/fundus of stomach ( OR 5.656 95%CI: 2.291-13.964, P<0.001) , body of stomach(OR 2.667 95%CI: 1.048-6.785, P=0.040) and > 2cm in size (OR 2.761 95%CI: 1.229-6.205, P=0.014) were independent risk factors for the operation time longer than 120 min. Conclusion Lesions located in the cardia/fundus and body of stomach and > 2cm in size were independent risk factors for a long operation time of ESD. It may be very useful to predict the operation time preoperatively.