Multifield coupling among gas flow, heat transfer, structure deformation and flight control is an important phenomenon for hypersonic vehicle. The coupling mechanism can be simplified according to simulation purpose. Typical simulation tests for different phases of hypersonic vehicle guidance, navigation and control (GNC) system design process are presented and the coupling boundaries are also given. Multifield coupling simulation time advancement scheme is proposed and calculation method for each field is presented. Multifield coupling simulation platform design method methodology is presented and an integrated numerical simulation platform prototype, consisting of geometry configuration design, mesh grid generation, trajectory optimization, GNC, aero-thermo-elastic coupling calculation, simulation results visualization and analysis software is designed. The functions of CSC-MPCSim are demonstrated through modeling and simulation of a flight vehicle with a configuration similar to X-43 hypersonic flight vehicle designed by NASA of the USA.