Abstract: As a kind of energetic material, propellant can be decomposed and heat can be generated. If the heat is not released in time but is accumulated,self-ignition would take place. For example, the self-ignition of two kinds of propellants stored in a experimental site was reported.It is proposed that self-ignition of one of them took place first and ignited the other. In this paper, two kinds of propellants self-ignition of which had taken place are studied numerically.The mathematical model of heat accumulation is established under the condition of heat insulation.The self-ignition time is calculated,and the result is discussed and analyzed. It is determined that self-ignition took place in propellant No.1 first, then propellant No.2 was ignited. The critical temperatures of two kinds of propellants under the condition of heat insulation are obtained.