Tool path generation, post-processing and verification and simulation of NC program are key technologies which are investigated in this research for manufacturing impellers. Generation of tool path aims at producing the cutting tool path. Post-processing transforms the cutter location file (CLSF file) of the tool path to the NC code which NC machine can recognize. Verification and simulation of NC program aims at proving the accuracy of program, thus the interference and collision can be avoided. When tool path is planned, increasing the machining efficiency during the rough and semi-finish milling process is the main consideration. Increasing machining accuracy is an important consideration for final finish milling.