In order to accurately study the flow field of high-temperature, high-pressure and high-speed gas jet passing through muzzle brake during gun launching, the two-phase flow field of muzzle brake based on moving grid was numerically simulated. Using FLUENT software, the flow field model of muzzle brake was established by using smoothing and reconstructing unstructured dynamic mesh updating method and structured/unstructured hybrid mesh technology, and the effects of two-phase flow field coupled by solid particles and gas phase in gas jet and single gas phase flow field on muzzle brake were compared and analyzed. The results show that there are obvious differences in pressure distribution between two-phase flow field and pure gas-phase flow field, which can provide some reference for the structural design and optimization of muzzle brake.