Objective To evaluate the clinical effect of retroanal midline incision and dilatation combined with anal sinus incision and drainage and lateral internal sphincter incision in patients with chronic anal fissure. Methods ?A total of 70 patients with chronic anal fissure admitted to Qingdao Chengyang District People's Hospital from December 2019 to December 2020 were selected and divided into experimental group and control group according to random number table method，with 35 cases in each group. The control group was treated with lateral internal sphincter resection，and the experimental group was treated with retroanal midline incision and dilation combined with anal sinus incision and drainage. The indexes of inflammatory factors，operating-related indexes，pain scores before and after surgery and the clinical efficacy of the two groups were compared. Results?The c-reactive protein，interleukin 6 and tumor necrosis factor alpha levels of two groups of patients before surgery were no statistically significant difference（P ＞ 0.05），the inflammatory factor levels after the surgery of two groups were lower than before，and the experimental group’s inflammatory factor levels all lower than the control group，the difference was statistically significant?（P ＜ 0.05）. There was no significant difference in operation time between the two groups（P ＞0.05）. The healing time and hospitalization time of the experimental group were shorter than those of the control group?（P ＜ 0.05）. There was no significant difference in score of pain between the two groups?（P ＞0.05）.The score of pain in the experimental group was lower than that in the control group on day 3 and 7 after surgery，and the difference was statistically significant?（P ＜ 0.05）. The clinical efficacy of patients in the experimental group?（94.29%）was higher than that in the control group?（74.29%），and the difference was statistically significant?（P ＜ 0.05）.Conclusion?In patients with chronic anal fissure，the treatment effect of retroanal midline incision and dilatation combined with anal sinus incision and drainage is significant，which can reduce the level of inflammatory factors in patients and promote postoperative recovery，and the level of postoperative pain in patients is relatively low.