In the present study, the plume exhausted from a satellite thruster is numerically investigated by employing the DSMC method. To do this, an axissymmetric DSMC code using unstructured grid system has been developed and validated through the comparison with the experimental results. Then, this code was applied to the study of plume from a practical thruster nozzle. As a result, the rarefied flow characteristics of plume such as strong nonequilibrium near nozzle exit, large back flow region, species separation, etc., have been confirmed.