Based on thermodynamics and internal ballistic theory, the energy characteristics and internal ballistic of dynamic infrared decoys are analyzed, and the mathematical models for the energy characteristics and internal ballistic of dynamic infrared decoys are established. Taking the formula of AP-PTFE-Mg-Al as an example, the detailed calculations and analysis are carried out for dynamic infrared decoys. The combustion heat, total enthalpy and entropy of the products, as well as the theoretical specific impulse and characteristic velocity of the engine of the dynamic infrared decoys are obtained. By using a self-programming with the Runge-Kutta method, the curves of pressure variation with time at different working stages are obtained. A method and theoretical reference are provided for the design of dynamic infrared decoys.