Abstract: Objective To investigate the efficacy and safety of endoscopic subcucosal dissection (ESD) in treatment of colorectal carcinoma in situ and precancerous lesions. Methods The data of 25 patients with colorectal carcinoma in situ and precancerous lesions who were treated with ESD from June 2016 to February 2018 was analyzed and evaluated the safety and efficacy of ESD. Results 25 cases of carcinoma in situ and precancerous lesions ranged from 1.1 ~ 6.9 cm in size with an average of 3.2 cm, and the operation time was 35 ~ 240 minutes with an average of 85 minutes. One-time complete resection of lesions was performed in 21 patients and the complete resection rate was 84.0% (21/25). 3 cases of high-frequency electrical snares were removed by fractionation, and 1 case of intraoperative hemorrhage was transferred to surgery. No perforation occurred in all these cases, delayed bleeding occurred in 2 cases, and endoscopic hemostasis was successful. All these patients were followed up for 3 months and the wound healing rate was 100.0%. The average follow-up period was 6 months and there was no residual or recurrence locally. Conclution ESD is a safe and effective treatment for the treatment of colorectal carcinoma in situ and precancerous lesions, which is worth clinical extension.