Background: Suprasphincteric anal fistula is a type of high anal fistula. The traditional method of cutting seton (CS) has a high recurrence rate and can cause severe damage to the anal sphincter and anal incontinence. The combination of loose and cutting seton is a novel method developed on the basis of the traditional cutting seton technique, and has already been adopted by some clinicians in China. This study will examine the effectiveness and safety of the loose combined cutting seton (LCCS) technique for the treatment of suprasphincteric anal fistulas. Methods: This is a single-blinded randomized controlled trial conducted in the Anorectal Department of the China-Japan Friendship Hospital. A total of 76 patients diagnosed with suprasphincteric anal fistula will be randomly divided into two groups. One group will be treated with the LCCS method (the LCCS group; n=38) and the other group will be treated with the traditional CS method (the CS group; n=38). There will be 3 intervention periods, including the screening period, the surgical treatment period, and the postoperative follow-up period. Postoperative follow-up will be carried out on days 3, 5, 7, 14, 21, 28, 90, 180, and 365 after the operation. The main outcome measures are the complete cure rate of postoperative wounds and fistulas, the long-term recurrence rate, and evaluation of postoperative anal function (Wexner anal function assessment and anal function questionnaire). The secondary outcomes are the visual analogue scale (VAS) score for postoperative pain, pressure measurements of the anal canal and rectum before and after treatment, and the incidence of adverse events. All statistical results will be analyzed using the SPSS software 21.0 version. P values <0.05 will be considered statistically significant. Discussion: This research introduces a novel method for the treatment of suprasphincteric anal fistulas. The LCCS method will be compared with the traditional CS method in terms of safety and efficacy. If the LCCS technique is a safe and effective treatment for suprasphincteric anal fistula, its clinical application should be promoted.