The inclusion defect in fluoride crystals significantly affects optical quality， and the formation of such defect is mainly determined by the shape of crystal interface and growth rate when using Bridgman method. This article focuses on the technique of Bridgman method， and intends to study the influence of thermal field on crystal growth rate and interface shape through numerical simulations， in an attempt to understand the underlying physics that enable the formation of a slightly convex interface shape and prolonging stable growth stage as well as to achive an effective inclusion defect control strategy. Numerical results show that the formation of interfaces with high convexity during fluoride crystal growth is mainly due to the radial heat absorption near the interface caused by internal radiation heat transfer characteristics. Increasing the length of the adiabatic block can reduce the growth rate in the initial stage and effectively reduce the interface convexity during the stable growth. Raising the temperature of the upper and lower heaters can shorten the initial unstable growth zone and effectively reduce the interface convexity during the stable growth. For the growth of large-sized or multi-crucible crystals， there exists a large radial temperature gradient， this means that the crystal growth interface is too convex. By increasing the temperature at the bottom of upper heater and adding heat dissipation openings in the adiabatic block， it is possible to establish a slightly convex interface shape which is unfavorable to inclusion defect formation.