Abstract: The FLUENT6.1 software was applied to simulate the supersonic flow in micro convergent-divergent nozzle with 5.4 expansion ratios.The simulation was complemented by computing steady two-dimensional Navier-Stokes equations to study the effect of mass x velocity and total pressure from throat,which has arc or not and different throat arc radius.Also,the fluent mass and thrust force effects were studied.It is observed by the study that x orientation mass velocity of thrust exit and thrust force are effected by the throat which has arc or not and throat arc radius.With the increase of throat Reynolds,the corresponding throat radius for the maximal fluent mass and thrust force increases accordingly.