The preparation of graphene by silicon carbide (SiC) decomposition is compatible with the current mainstream device preparation technology and has a great application prospect. In this paper, VR-PVT software is used for theoretical simulation. The flat temperature field conducive to the uniform growth of large-size graphene is obtained by adjusting the heat preservation and insulation device, heat source setting, heating power and crucible design in the growth system. High quality 6-inch homogeneous bilayer graphene is grown on 6-inch 4H-SiC (0001) surfaces with optimized temperature field and suitable etching and growth process.