Abstract: In order to improve the efficiency and quality of NC programming efficiency and quality for slender planes, an automatic NC programming method was studied. The process information of slender plane feature was obtained in the MBD model and the feature image was generated. The machining reference trajectory extracted from the feature image was optimized. The optimized reference trajectory was projected onto the original feature plane in order to generate tool path and NC codes automatically. Finally, the prototype system based on this method was developed on the NX platform and the key parts of a marine diesel engine were used as the tested objects in this system. The results showed that this method realized the automatic generation of NC programming and reduced the frequent human-cam interaction effectively. Moreover, the NC codes generated by this method, compared with traditional programming method, reduced the processing time by nearly 65% on average.