Thermal radiation from a high-temperature source is the primary cause of energetic material explosions. However, current research cannot meet the need to prevent thermal radiation-caused explosions. This paper proposes a novel numerical calculation model for temperature response and the chemical reaction of energetic materials under thermal radiation based on the physical mechanisms and evolution of the thermal effect during the chain explosion accident. This model is essential for rapidly evaluating the effect of thermal radiation in chain explosion accidents. The numerical model in this study efficiently obtained the thermal response of energetic materials under thermal radiation, as well as the critical conditions for energetic material explosion under thermal radiation. The results reveal that heat conduction is difficult to cause the explosion of ammonium nitrate, but thermal radiation can. The critical temperature of explosion for ammonium nitrate is 1668 K, the critical duration is 15.93 s, and the critical distance is 7.85 m. The temperature, duration, and radiation distance of the heat source are crucial factors that induce the ammonium nitrate explosion. Firefighters must cover and protect ammonium nitrate within 7200 s and 15.93 s, respectively, when the external heat flow absorbed by the material is 2.688 kW/m2 and 28 kW/m2. The model proposed in this paper can predict the effect of thermal radiation once the heat source parameters are known. Besides, combined with machine learning, the model can also predict the heat source parameters once the parameters of the thermal radiation effect are known. Compared with the current numerical models to evaluate the effect of thermal radiation, the numerical model presented in this paper can evaluate the effect of thermal radiation in engineering more efficiently and has broad application prospects.