Abstract: Objective To investigate the influence of conventional and modified LIFT on clinical efficacy for short-term and anal function of patients with complex anal fistula.Methods 94 patients with complex anal fistula were chosen in the period from January 2016 to January 2018 in our hospital and randomly divided into two groups including control group（47 patients）with conventional LIFT operation and modified group（47 patients）with modified LIFT operation;and the surgery-related clinical indicators，clinical efficacy for short-term，pain VAS score after operation，Wexner score of anal incontinence before and after surgery，anal and rectal pressure before and after surgery and complications incidence after surgery of both groups were compared.Results There was no significant difference in the surgery-related clinical indicators between 2 groups （P>0.05）.The clinical efficacy for short-term of control group and modified group were separately 76.60%，93.62%.The clinical efficacy for shortterm of modified group were significant better than control group（P<0.05）.There was no significant difference in the pain VAS score after operation and Wexner score of anal incontinence after surgery between 2 groups （P>0.05）.There was no significant difference in the anal and rectal pressure before and after surgery between 2 groups （P>0.05）.The incidence of intermuscular incision dehiscence infection and sphincter fistula of control group were separately 25.53%，14.89%.The incidence of intermuscular incision dehiscence infection and sphincter fistula of modified group were 14.89%，4.26%.The incidence of intermuscular incision dehiscence infection and sphincter fistula of modified group were significant lower than control group（P<0.05）.Conclusion Compared with conventional LIFT，modified LIFT in the treatment of patients with complex anal fistula can efficiently improve the overall clinical effect，promote the healing process of lesions，reduce the postoperative complications risk and not affect anal function.

Key words: ligation of intersphincter fistula, complex anal fistula, clinical efficacy for short-term, anal function