As one of the key components of nuclear power equipment, large nuclear power head has a complicate shape, great allowance of processing and difficult to produce. There is no any successful experience for reference. In this paper, one type of nuclear power head is our research object. We mainly researched on the NC processing programming of large nuclear power head and implemented processing simulation by alternative applying variety of processing methods, including calculation and simulation of tool path, generation of pre-processing files, and development of post-processor based on specific milling processing center, and the generation of NC codes. Finally, through Vericut, the simulation software platform, simulation verification of NC codes was implemented. The results indicated that the processing scheme was reasonable, NC codes were right and there was no phenomenon of over-cutting and under-cutting happening.