Abstract: Objective：To compare the efficacy of midline sphincterotomy plus anal sinus drainage or lateral incision of internal sphincter in chronic anal fissure.Methods：106 chronic anal fissure patients treated were selected and randomly assigned to two groups, 53 cases each group. The study group was treated with midline sphincterotomy plus anal sinus drainage; the control group was treated with lateral incision of internal sphincter. The therapeutic effect was compared.Results：The total effective rate in the study group and control group was 98.11% and 94.34%, without statistical differences (P＞0.05); the complication rate and recurrence rate in the study group was 5.66% and 7.55%, which was lower than that of control group (16.98%, 20.75%) (P＜0.05); the wound healing time and hospitalization time in the study group was shorter than control group (P＜0.05); before surgery, the VAS (visual analogue scale) scores and quality of life scores showed no statistical differences (P＞0.05); after surgery, the related scores in the study group were better than control group (P＜0.05).onclusion：The midline sphincterotomy plus anal sinus drainage or lateral incision of internal sphincter have its effect in chronic anal fissure patients, but the former can better shorten the treatment time, reduce the clinical trauma and recurrent rate, relieve the pain and increase the quality of life. 

Key words: lateral incision of internal sphincter, chronic anal fissure, anal sinus drainage, midline sphincterotomy