Objective To evaluate the curative effect and superiority of minimally invasive transanal surgery in the treatment of cancerate rectal adenoma and early rectal cancer by using CUSA.Method Local resection was clone in 15 patients with cancerate rectal adenoma or early rectal cancer,the tumours were excised intactly by 5 mm CUSA(submucosal or superficial muscularis),the incisions were closed by continuous suture in the lumen.Results All of the tumours were excised intactly,the incisal edges and funduses were all negative.The operation time was 30～180 min,average:60 min,the amount of bleeding during operation was 0～30 ml,average:10 ml.Complications:temporary fecal incontinence in 2 cases,acute urinary retention in 1 case.Pathology after operation:villous adenoma accompanied by high grade intra epithelial neoplasia in 8 cases,mixed adenoma in 2 cases,intra-mucosal carcinoma in 5 cases.15cases were followed up 4～48 months,averge 18 months,no tumour recur in original place.Conclusion Minimally invasive transanal surgery by CUSA is a safe and effective operation in the treatment of cancerate rectal adenoma and early rectal cancer.It can keep the anus and improve the quality of life.