Abstract: Numerical simulation is employed in calculation of the combustion processes in the rocket engine which uses liquid hydrogen and oxygen as propellants.A random spray model is used to describe the initial conditions of oxygen droplets.The evaporation rate of the oxygen droplets at high pressure is calculated by ZKS model.The Arrehnius model is adopted to compute the chemical reaction rates.PISO algorithm extended by the authors is used to calculate the spray combustion flow.The convection terms of the governing equations are discretized by a second-order upwind scheme.