With Fluent software, specific growth process of large size calcium fluoride crystals by the vertical Bridgman method was simulated and calculated. The heat transfer and the melt convection of crystal growth process were investigated. The difference of the thermal conductivity of solid phase, liquid phase and crucible has effect on axial temperature profile and axial temperature gradient profile along the centerline of the crucible and radial temperature profile and radial temperature gradient profile at the solid-liquid interface was analyzed. The results show that the effect of the melt convection heat transfer becomes weak with continuous crystal growth;The difference of the thermal conductivity of solid phase, liquid phase and crucible has important effect on axial temperature profile and axial temperature gradient profile along the centerline of the crucible and radial temperature profile and radial temperature gradient profile at the solid-liquid interface;Rate of crystallization are inconsistent with descent velocity of crucible.