The invention relates to a preparation method of high-performance activated carbon fibers, belonging to the technical field of carbon fibers. The method comprises the following steps: on a continuous activation facility, by using polyacrylonitrile-base fibers as the raw material, impregnating a chemical reagent on the surface of the raw material fibers, and preparing the high-performance activated carbon fibers, of which the specific area is not less than 1500m<2>.g<-1> and the tensile strength is not lower than 0.5 GPa, by the aid of a physical-chemical synergic activation process by using the vapor volume percent phi-vapor as the variable (the phi-vapor value is controlled within the range of 0.4-4.5*10<-4>). The method is simple, and has the advantages of high preparation efficiency and lower cost; and the obtained sample has high specific area and excellent mechanical properties, and can form products in various shapes so as to be applied to the fields of gas purification, sewage treatment and the like.