Objective:To observe the efficacy of hemisection and ligation surgery of lateral anal internal sphincter in the treatment of chronic anal fissure. Methods60 patients with chronic anal fissure were randomly divided into the treatment group and control group,30 cases in each group. The control group was treated with anal internal sphincterotomy and the treatment group was treated with hemisection and ligation surgery of lateral anal internal sphincter. The postoperative pain and bleeding,wound area and wound healing time were observed and compared between the two groups.  Results:①On the 1st,3rd and 7th day after the operation,the pain and bleeding scores in the treatment group were lower than those in the control group at the corresponding period (P<0.05). ②On the 1st,3rd,7th and 14th day after the operation,the wound area score in the treatment group was lower than that in the control group at the corresponding period (P<0.05). ③There was statistically significant difference on the wound healing time between the two groups (P<0.05).  Conclusion:The hemisection and ligation surgery of lateral anal internal sphincter in the treatment of chronic anal fissure can reduce the bleeding and relieve the pain after surgery,diminish the wound area and shorten the wound healing time.