A path planning processing method of a ruled surface impeller cutter relates to a cutter path planning processing method. The invention solves the problems of the prior numerical control processing method of an impeller part, the problem are that a whole processing technology for processing a integral type ruled surface impeller is not proposed, the calculating method of the point of a knife centre or the point of a knifepoint is not given, the processing cutting efficiency is low, the operation is complex and the degree of automation is low and the five-axis processing of the ruled surface impeller can not be realized etc. The main steps of the method are the establishment of the calculator assistant manufacturing model CAM of an impeller part, the calculation of the vector of a cutter shaft, the calculation of the point of the knife centre, the planning of whole cutter path and the achievement of the processing of the impeller part. The method of the invention solves the problem of the five-axis processing of the ruled surface impeller and has the advantages of high processing cutting efficiency, easy operation and high degree of automation The ruled surface impeller processed by the method has the characteristics of orderly linage of flow passage, symmetrical structure and the uniform distribution of cutter path at the surface of the flow passage, thus reducing the workload of subsequent polishing processing greatly.