1.Domestic classification: 1.Low anal fistula Low simple anal fistula: the internal port is in the anal fossa, and only one fistula passage is through the subcutaneous or superficial part of the external sphincter, which is connected with the skin. Low complex anal fistula: there are more than two internal or external ports, the fistula channel through the lower part of the external sphincter skin and shallow. 2, high anal fistula high simple anal fistula: internal mouth in the anal fossa, there is only one fistula tract, walking above the deep layer of the external sphincter. High complex anal fistula: there are more than two external ports, connected to the internal port through the fistula or with a branched cavity, and its supervisor passes above the deep layer of the external sphincter. The classification of anal fistula depends on the relationship between the fistula and the anal sphincter and is divided into: intersphincter type, trans-sphincter type, over-sphincter type, and external sphincter type. When the fistula crosses more than 30 to 50% of the external sphincter (high intersphincter, supra-sphincter, external sphincter), female anterior fistula, multiple fistulas, recurrent fistulas, or fistulas with anal incontinence, or fistulas that may cause anal incontinence after treatment are considered complex anal fistulas.