Objective  To investigate the correlation between obesity and pathological changes after radical prostatectomy. Methods  A retrospective analysis of 120 patients undergoing radical prostatectomy from January 2014 to January 2019 was performed. The patient's age, height, weight, prostate volume, biopsy pathological results, preoperative PSA levels, and postoperative pathological results were collected. Patients were divided into three groups according to BMI, normal group(185 kg/m²≤BMI<24 kg/m²), super-recombination(24 kg/m²≤BMI<28 kg/m²), obesity group(BMI≥28 kg/m²) .Results  This study included 120 patients. There were 30 cases in the normal group, 66 cases in the super group, and 24 cases in the obesity group. After radical prostatectomy, the Gleason score was higher in the obesity group than in the other groups(P<0.01). Forty-eight patients were diagnosed as locally advanced prostate cancer, including 6(20.00%) in BMI normal group, 27(40.91%) in overweight group and 15(62.50%) in obesity group. The difference was statistically significant(P<0.01). Gleason score was upgraded in 28 patients, including 5(1667%) in normal BMI group, 13(19.70%) in overweight group and 10(41.67%) in obesity group, with significant difference(P=0.04). Postoperative margin was positive in 30 patients, including 4(13.33%) in the normal BMI group, 17 (22.73%) in the overweight group and 9(37.50%) in the obesity group(P=0.04). Conclusions  Patients with obesity have a higher Gleason score and pathological stage after radical prostatectomy, and have a higher rate of positive margin and a higher rate of Gleason score upgrade.