Aiming at open-inlet mode ring focusing thruster,issues including thrust,impulse coupling coefficient and thermal damage on the cowl are numerical simulating investigated by altering the focus location.The results indicate that the performance of thruster deeply depends on the focus location.When the focus is located far from the cowl,the thrust occurs earlier,the impulse coupling coefficient is larger and the thermal damage risk of the cowl is lower than those of laser focusing on the cowl.In addition,in order to prevent the shockwave rushing out of the inlet and inducing additional drag to the thruster,the length and inclination of cowl to the inflow should be steeper in design of the thruster.