To accurately analyze the interior ballistic performance and launch overload of image terminal guided projectiles， the connotative essence of the firing with different charge numbers was investigated based on the characteristics and working principles of the adaptive launch platform and launch charge. The interior ballistic two-phase flow model for image terminal guided projectile was established， and its rationality was verified through simulations and measured data under two different working conditions. Building on this， the evolution laws of pressure fluctuation and projectile motion in the bore of a certain type of image terminal guided projectile with different charge numbers were analyzed using the verified interior ballistic two-phase flow model. Furthermore， the launch overload characteristics of this type of image terminal guided projectile with different charge numbers were studied through the established engineering calculation model of launch overload. The results show that the relative errors of the maximum pressure at the bottom of the bore and the initial velocity of the projectile between two verification conditions are less than 2%， and the variation laws of the pressure at the bottom of the bore and the pressure wave in the bore with time are highly consistent between simulation and measurement. The internal ballistic performance and launch overload variation laws of the image terminal guided projectile with different charges obtained from the verified model are consistent with the general laws of the actual launching process.