To provide corresponding reference for choosing reasonable calculation model in numerical simulation of two-phase flow, the difference and suitable situation of equilibrium flow and non-equilibrium flow were studied through numerical simulation. The ke turbulence model under high Reynolds number, two-fluid model and full-speed SIMPLE method were used to simulate equilibrium flow and nonequilibrium flow in solid rocket motors. Calculation results show that the difference existing in the expansion nozzle segment, and the difference is more obvious with increase of expansion ratio. We can conclude that the simulation result of two-phase is more accurate when the expansion ratio of nozzle is relatively large.