In order to evaluate the thermal safety of melt-cast explosive process, a calculation method of thermal explosion critical process temperature is described. The time to ignition for various process temperatures are calculated by using the performance data of DNTF. Through comparing the calculated value and practical process time, the level of process thermal safety can be classified and critical process temperature can be obtained. The results show that the process of DNTF is safe under normal condition. However, the risk level of thermal explosion will increase as the explosion throughput rises. The calculation method has important significance for the preparation of the melt-cast explosion process parameters.