Abstract：A straight-tube type high pressure air ejection device was studied in this paper, aiming at impacts that structure parameters, gas source characteristics and environmental factors on the interior ballistic characteristics of ejection system and considering the real gas effects of compressed air, an interior ballistic mathematical model of high-pressure-air ejection was established. What's more, the influence law of multiple variables including air pressure, the control valve size and initial temperature to interior ballistic characteristic curves were simulated, calculated and analyzed and it was concluded that these three parameters influence the interior ballistic parameters differently. Finally, it will benefit the missile ejection as these parameters being within a reasonable range and work cooperatively.