4 kinds of muzzle devices with different structures were designed to solve the problem of vibration caused by high muzzle pressure during gun firing. The pressure around the device was reduced by introducing the propellant gas into the device to expand and then exhaust, and the numerical simulation of the muzzle flow field with different devices was carried out by combining with the dynamic mesh technology, and the effect of each device was determined by comparing the pressure drop around the muzzle without the device, and the pressure reduction effect of different devices was analyzed according to the numerical simulation results. The calculation results show that the pressure around the muzzle decreases obviously after installing the muzzle device, which has certain reference value for the further design of the device structure.