The invention belongs to the AC power distribution network fault diagnosis field and particularly relates to an AC distribution line fault positioning method. Through determining regional faults and introducing the vertex-to-arc load and the area load, the simple minimum distribution area separation algorithm is given, search steps of an overheated region are discussed in detail, and correspondingcountermeasures are given for the situation that the fault information of a feeder measurement and control terminal is small and incomplete. The method is advantaged in that as shown in example analysis, the new method has simple reasoning, good fault tolerance, can accurately measure the fault degree and has high practical value.