Objective: To explore the correlation between obesity and the risk of colorectal adenoma, so as to provide theoretic evidence for the intervention of the high-risk population for colorectal cancer. Methods: Based on the Screen Project of Early Diagnosis and Treatment of Colorectal Cancer in Jiashan County, from August 2012 to March 2018, the results of colonoscopy and body measurement information of the high-risk population for colorectal cancer were collected. According to the results of colonoscopy, 3 895 patients with colorectal adenoma and 11 232 healthy controls were enrolled. Multivariate logistic regression was used to analyze the correlation between overweight (body mass index (BMI) 24.0 to 27.9 kg/m²), obesity (BMI≥28.0 kg/m²) and the risk of colorectal adenoma. Results: After adjusting for gender and age, compared with that of individuals with normal weight (BMI 18.5 to 23.9 kg/m²), the risk of colorectal adenoma of obese patients increased by 36% (odds ratio (OR)=1.36, 95% confidence interval (CI) 1.18 to 1.56). After stratifing by gender, compared with that of individuals with normal weight, the risk of colorectal adenoma of obese males increased by 30% (OR=1.30, 95%CI 1.07 to 1.59), the risk of colorectal adenoma of overweight females and obese females increased by 15% (OR=1.15, 95%CI 1.01 to 1.31) and 40% (OR=1.40, 95%CI 1.14 to 1.71), respectively. After stratifing by age, compared with that of individuals with normal weight, the risk of colorectal adenoma of obese patients aged between 40 and 59 years increased by 31% (OR=1.31, 95%CI 1.07 to 1.61), and the risk of colorectal adenoma of overweight and obese patients aged between 60 and 74 years increased by 13% (OR=1.13, 95%CI 1.01 to 1.27) and 39% (OR=1.39, 95%CI 1.15 to 1.70), respectively. The results of subgroup analysis according to pathological types indicated that the risk of non-advanced adenoma and advanced adenoma of obese patients increased by 35% (OR=1.35, 95%CI 1.16 to 1.57) and 39% (OR=1.39, 95%CI 1.06 to 1.83), respectively. Conclusions Obesity is correlated with colorectal adenoma, which is more significant in women, individuals aged between 60 and 74 years and advanced adenoma. The intervention of high-risk population for colorectal cancer should include body mass control.