The modeling of chemical oxygen iodine laser power using a simplified saturation model is established. The main factors influencing the power of chemical oxygen iodine laser have been studied theoretically. According to the testing parameter of chemical oxygen iodine laser, the power stability caused by chlorine and iodine pressure has been analyzed. It is found that the root mean square (RMS) of chlorine and iodine venturitube pressure becomes small as the laser time increasing between 1 and 6 seconds, at the same time, the more RMS of chlorine, iodine venturitube pressure, the more RMS of chemical oxygen iodine laser power. Chemical oxygen iodine laser power stabilization increases by improving the pressure stabilization of chlorine and iodine venturitube.