Objective：To analyze the clinicopathological features and carcinogenesis risk factors of colorectal laterally spreading tumor（LST） including 15 cases with multiple lesions. Methods：The clinical data of 209 patients with LST diagnosed by colonoscopy in the Department of Gastroenterology，the First Affiliated Hospital of Nanjing Medical University from January 2010 to December 2020 were retrospectively analyzed. Results：A total of 222 LST were included in the study， including 30（13.5%） LST-G-homogenous type （LST-G-H），64（28.8%） LST-G-mixed type（LST-G-M），118（53.2%） LST-NG-flat elevated type（LST-NG-F） and 10（4.5%） LST-NG-peseudodepressed（LST-NG-PD）. A total of 15 multiple LST，occurred in the right colon（80.0%，12/15），the pathology was mainly low-grade dysplasia（66.7%，10/15），with endoscopic submucosal dissection（ESD） as the main treatment（60.0%，9/15）. Patients with a history of colon polyps were more likely to appear multiple LST. Multiple LST were more common in LST-G-H type，and single LST were more common in LST-NG-F type. Multivariate Logistic regression analysis showed that the size of lessions > 20 mm and the junior endoscopic physicians（OR 5.074，95%CI 2.011~12.801，P < 0.05） were independent risk factors for LST carcinogenesis，in which the size of lessions ≥40 mm（OR 5.468，95%CI 1.792~16.684，P < 0.05） had a higher risk of carcinogenesis. Conclusion：The size of lessions > 20 mm and the junior endoscopic physicians were independent risk factors for LST carcinogenesis. Patients with a history of colon polyps were more likely to appear multiple LST. Multiple LST were more common in LST-G-H type， and single LST were more common in LST-NG-F type.