Abstract: To accurately predict the performance of FMMR,under different propellant and working conditions,Direct simulation Monte Carlo method was used to simulate the gas flow in FMMR.The thrust and specific impulse of FMMR were calculated,and the influence of propellant types,working pressure as well as heating temperature on the performance of FMMR was studied.Results of calculation and analysis show that the propellant kind has no effect on thrust,while specific impulse rapidly increases with the decreasing of propellant molecule weight;the specific impulse of FMMR increases with the height of working pressure and heating temperature,and thrust increases with the increasing of the working pressure but decreases with the increasing of the heating temperature.