In order to reduce the recoil kinetic energy of cannon barrel and advance impact of muzzle brake, a method studying the structure characteristics of muzzle brake using computational fluid dynamics (CFD) method is proposed, and the formulas of the structure characteristics under steady and unsteady flow are derived respectively. Then, the structure characteristics of three different muzzle brakes are calculated under steady flow condition, but they have different inlet total pressure or total temperature. For one of the three kinds of muzzle brake, the structure characteristics under linear and nonlinear unsteady flow inlet conditions are calculated separately. Calculation results indicate that the inlet total pressure or the total temperature or whether it’s steady flow or unsteady flow has no influence on the structure characteristi