Charge temperature is one of the main tactical and technical indices for a large caliber self-propelled gun, and is a critical firing datum affecting the projectile muzzle velocity and gun firing accuracy. In this paper, on the basis of analyzing the heat transfer character of propellant, an unsteady-state heat conduction model describing the variation of the charge temperature is built and the finite-difference implicit schemes are theoretically deduced using the volume equilibrium method for numerical simulation. Comparing simulation curves with experiment results indicates that the physical models used reflect the real-time change process of the charge temperature with the environment temperature. A noncontact automatic online charge temperature measurement unit is developed. This unit can accurately measure the temperature field and real-time average temperature of the charge for all charge zones placed in a combat vehicle and simultaneously transfer the temperature information to the gunner task terminal computer through a controller area network (CAN) bus interface for trajectory calculation and firing data correction, ensuring the weapon system meets the requirements of digitalization and informatization.