The customization process of postprocessing of FIDIA fiveaxis vertical machining center was studied, and the correctness of the post-processing was verified by virtual simulation technology. Postprocessing for the FIDIA C1 system was customized with the post-builder of NX. In order to verify the correctness of post-processing, a simplified machine model was established in NX. The various parts of the machine were exported to VERICUT in STL format file, and corresponding configuration was made in VERICUT to complete the construction of virtual simulation environment. With the mouse model as the processing object, the tool path was created in NX. The tool path source files were converted into NC codes that the machine tool could recognize by the customized postprocessing, and simulated processing was performed in the virtual simulation environment. The NC program was transmitted to machine tools for actual processing after the verification was correct. The results show that the virtual simulation technology can effectively avoid machine collision caused by improper postprocessing customization, ensuring safe and efficient operation of the machine.