Abstract: A cook-off simulation model for composite charge (interior JO-9159/exterior JB-9014) was established to investigate the characteristics of explosive thermal reaction at different heating rates. The thermal responses of the composite charges with different structures were calculated by the finite element program LS-DYNA3D. The simulation results were verified by the experiments. Based on the available model, the calculations were conducted to simulate the cook-off tests for the composite charges at heating rates of 5 K/h, 3 K/min and 10 K/min. The results show that the heating rate and charge structure have great effect on the ignition time and position for the composite charge explosive. The ignition time decreases and the ignition position moves from the center to the two ends of the cylinder edge with the increase of the heating rate. The thermal stability depends on the interior high explosive when the heating rate is relatively low. The thermal stability is similar to the single insensitive explosive when the heating rate is relatively high. Therefore, only at higher heating rate, this kind of composite charge structure can improve the explosive power and thermal stability.