Objective To investigate the effect of modified ligation of the intersphincteric fistula tract (LIFT) on anal function of high complex anal fistula (CAF). Methods A total of 62 patients with high CAF treated in Yichun Hospital of Traditional Chinese Medicine in Jiangxi Province from February 2020 to January 2021 were selected as the research objects.They were divided into observation group(31 cases)and control group(31 cases)by random number table method.The patients in the observation group were treated with modified LIFT, and the patients in the control group were treated with incision and thread hanging. They were followed up for 8 months. The treatment effect, clinical related indexes,anal function, complications and recurrence of the two groups were compared. Results There was no significant difference in the total effective rate between the two groups (P>0.05). The operation time of the observation group was longer than that of the control group, the wound healing time and hospital stay were shorter than those of the control group,and the visual analogue scale (VAS) score and Wexner score were lower than those of the control group, with statistically significant differences (P<0.05). The total incidence rate and recurrence rate of complications in the observation group were lower than those in the control group, with statistically significant differences (P<0.05). Conclusion The modified LIFT can achieve the same effect as incision and thread hanging in the treatment of high CAF, and has more advantages in shortening the wound healing time, reducing pain and protecting anal function, and can reduce complications and disease recurrence.