In 1985, through observational studies of anal fistula tracts, we proposed an important role for the anal sphincter in the pathogenesis of anal fistula. Through observation of 48 intraoperative anal fistulae with intact fistulae, it was found that the main lesions were located in the inter- or intramuscular portion of the fistulae penetrating through the anal sphincter and in the submucosal portion of the rectum. The lesions were mainly localized fistula stenoses and infected abscesses in front of the stenoses, the latter showing incomplete walls, localized enlargement in the form of a pus cavity with a purple color, and containing necrotic tissue, pus moss and a small amount of pus. Three types of fistulas are classified according to the pathological changes in the fistulae that penetrate the anal sphincter: stenotic, abscess and mixed. In fistulas lateral to the anal sphincter, 75% show a smooth inner wall with minimal inflammation; 25% have a pus cavity on the fistula or are connected to a pus cavity. The latter had a short history of anal fistula or a recent episode of perianal infection. No fistula without penetration through the anal sphincter was found in this group of cases. Instead, the internal orifice was either a small depression or a small protrusion of hyperplasia that had completely lost the anatomical structure of the original anal saphenous fossa. We conducted a study and summary of “proximal fistulotomy” for the treatment of complex anal fistulas based on the idea that the anal sphincter plays an important role in the pathogenesis of anal fistulas, as proposed in the study of the pathogenesis of anal fistulas, and provided a clear definition of the main tract of anal fistulas. The main tract is the section of the fistula that connects to the internal orifice and passes through the anal sphincter, and it can be one or more. The so-called “proximal fistulotomy” is a complete dissection of this main tract. Therefore, we believe that the course, number, and exact location of the internal opening of the main tract through the anal sphincter must be carefully investigated during the procedure. An open fistula can be healed by simply enlarging the external opening appropriately, scratching the canal, and adequately draining it for several days. The “proximal fistulotomy” is a new, standardized surgical treatment. It is a simple procedure that does not require too much effort to dispose of the open fistula and has little impact on the normal anatomical position and function of the anus. Thus, it has the characteristics of small trauma, short treatment course, satisfactory efficacy, easy operation and promotion.