Abstract: The two-dimensional axisymmetric subsonic-transonic-supersonic flow in an experimental arcjet thruster is simulated numerically using flux vector splitting method.The profiles of density,velocity,temperature,pressure and Mach number can be obtained by the computation.The computation grid and some computed results are given here.The test equipment such as power supply system,ignition system,propellant supply system,arcjet thruster,thrust measuring device and vacuum system are introduced briefly.Some working phenomena of the arcjet are observed and discussed.Three different kinds of instability appeared in the process of the experiments.Except some important parameters are measured,it is found that the operating stability of Argon is better than that of Nitrogen.