Abstract: In order to provide analysis results for fault diagnosis in a tail pipe nozzle to make some suggestions,two phase flow field is studied for a tail pipe nozzle by using the trajectory model and finite volume method to obtain the gas temperature and Mach number distributions,and to simulate the collision between the wall and different size particles under different total pressures.The calculation results show that there exists a point on the pipe inner wall where large size particles collide with wall intensively,giving rise to the tail pipe fault as a main cause,higher total pressure makes more collisions between particles and wall while larger size particles provoke makes more collisions.Accordingly some suggestions are prompted to enhance the reliability of heat resistant construction for a tail pipe nozzle.