An Euler-Lagrange method was used to describe gas-liquid two-phase flow in high temperature and high pressure supersonic cross flow of gas-steam launching system.The gas phase flow field was simulated by solving the Navier-Stokes equations using RK (Runge-Kutta)-AUSM+ (advection upstream splitting method+) scheme.A particle trajectory model was used to represent the liquid phase.The source terms were added to the gas phase conservation equations to simulate the coupling of two-phase.Several applications were calculated to analyze the droplet evaporation and the influence on gas flow field and energy output.The conclusions are useful to design and optimize the gas-steam launching system and energy regulation.