Abstract: Characteristics of several missile eject power systems were introduced and compared. The interior ballistic models of these power systems were designed on the basis of assumed conditions. And the programs were work out to predict and compare the interior ballistic performance about a certain missile and targets. The results of different power systems show the state parameters rules of working fluid with respect to the time in launching canister and the missile acceleration, velocity and displacement changing rules. The performance curves were compared and analyzed, which indicate that the working fluid flux of gas-steam eject power system is smaller, its structure is simpler and the pressure and acceleration change smoothly, the temperature is moderate, the missile velocity and displacement increase quickly, the launching time is shorter. Its interior ballistic parameters are better than others and have a great developing prospect. These results can provide a reference to design and select project of missile eject power systems.