Abstract: In order to study the influences of particles on gas flow in nozzle of solid rocket motor and the rules of particles flowing at different sizes,an Eulerian-Lagrangian approach was employed,Particle trajectory model was used for particle phase and compressible N-S equations were solved.MUSCL-Roe total variation diminishing(TVD) scheme with high order accuracy,and two-stage,time-stepping Runge-Kutta method with TVD character have been used to solve two-dimensional axis symmetric compressible N-S equations by a home codes "Solve2D".Simulation results indicate that the influence of particle primarily lies in throat and expansion segments of nozzle.Compared to pure gas flow,Mach numbers decreased along centerline,and the reduction became larger with smaller size particle.The gas temperature increased in two-phase flow,and the enhancement became higher with smaller size particles.The region without particles was smaller with smaller size particles.Big size particles had serious collision with wall of convergent region,and the region without particles was larger.