The invention discloses a five-axis linkage numerical control (NC) machining post processor and a processing method thereof, and relates to a post processor for an NC machining program and a processing method. The processor comprises computer program software which is used for processing a cutter location source file generated by a workpiece shape characteristic and a machining process, wherein the computer program software comprises a file management function module, a cutter management function module, a postprocessing function module, an NC file modification function module, a G code simulation function module, an NC file transmission function module, a coordinate system offset function module, an error compensation function module, a speed modification function module, a programming mode function module and a cutter-lifting and programming staring point function module. The processing method comprises the steps of setting a file, arranging a cutter, processing a programming mode, processing data of machine tool motion parameters, processing data of cutter dynamic cutting speed, outputting a G code file and the like. By the processor and the processing method, machining dynamic speed, speed compensation, non-linear error compensation and analog simulation of G code five-axis linkage can be realized.