Objective To investigate the effect of trans-sphincter space drainage on postoperative pain, anal function, and anal fistula formation rate in patients with high intramuscular posterior horseshoe shaped perianal abscess. Methods A total of 90 patients with high intramuscular posterior horseshoe shaped perianal abscess were selected from January 2020 to July 2023, and randomly divided into a study group and a control group with 45 cases in each group. The patients in the control group were treated with incision and thread-drawing, while those in the study group were treated with drainage through sphincter space. The two groups were compared in terms of pain [visual analogue scale （VAS） score], anal function （Wexner score）, and anal fistula formation rate. Results After surgery, the VAS score of the study group was significantly lower than that of the control group （P<0.05）, the Wexner score was lower （P<0.05）, and the incidence rate of anal fistula was also lower （P<0.05）. Conclusion Trans-sphincter space drainage surgery can effectively alleviate postoperative pain, improve anal function, and reduce the incidence of postoperative anal fistula in patients with high intramuscular horseshoe shaped perianal abscess.