Objective To analyze the pathological types of colorectal flat polyps after endoscopic mucosal resection (EMR),and explore the risk factors of high-risk fiat adenomatous polyps.Methods The retrospective case-control study was conducted.The clinicopathological data of 245 patients with colorectal fiat polyps who were admitted to the People's Hospital of Xinjiang Uygur Autonomous Region between February 2010 and April 2016 were collected.All the patients underwent EMR,and incision tissues were diagnosed by pathological examination.Observation indicators:(1) clinical features and results of pathological examination of flat polyps;(2) risk factors analysis of high-risk flat adenomatous polyps.Measurement data with normal distribution were represented as (x)±s.The univariate analysis and multivariate analysis were respectively done using the chi-square test and Logistic regression model.Results (1) Clinical features and results of pathological examination of flat polyps:flat polyps located in the cecum,ascending colon,transverse colon,descending colon,sigmoid colon and rectum were detected in 12,26,55,35,73 and 44 patients,respectively.Of 245 patients,153 were combined with multiple polyps.The diameter of fiat polyps was (0.9±0.8)cm.Results of pathological examination of 245 patients:108,40,18,25,14,3,12,12 and 13 patients were diagnosed with as tubular adenomas with low-grade intraepithelial neoplasias (LGINs),tubulovillous adenomas with LGINs,tubulovillous adenomas with high-grade intraepithelial neoplasias (HGINs),tubular adenomas with HGINs,adenocarcinomas (T1 stage),neuroendocrine tumors,serrated polyps,mucosal chronic inflammation and hyperplastic polyps,respectively.(2) Risk factors analysis of high-risk fiat adenomatous polyps:the results of univariate analysis showed that age,number and diameter of polyps were the related factors related factors affecting the occurrence of high-risk fiat adenomatous polyps (x2 =8.920,5.455,36.901,P＜0.05).The results of multivariate analysis showed that age ＞ 60 years old and diameter of polyps ＞ 1 cm were the independent risk factors affecting occurrence of high-risk fiat adenomatous polyps (Odds ratio =2.681,8.162,95％ confidence interval:1.481-4.856,3.786-17.597,P＜0.05).Conclusion The main colorectal fiat polyps are adenomatus polyps,and age ＞ 60 years old and diameter of polyps ＞1 cm are the independent risk factors affecting occurrence of high-risk fiat adenomatous polyps.