Due to the expensive software of full scope simulator and extensive work to model and debug, it spends a great deal manufacturing the full scope simulator. Meanwhile, the software of simulator used at home is mostly developed by other companies while domestic research about simulator focuses on the application of software. However, the core of the full scope simulator is software. In the paper, the full scope simulator platform and the core calculation model are developed with the parallel distributed simulation design, modularized structure, and the C-S framework. The nuclear power plant system program, physical computation program and and severe accident simulation used in simulation are modified based on these of the COSINE program package. The other calculation programs are designed, developed and verified independently. Finally, a fully autonomous simulation simulator, cosMuse is built.