Abstract: Mesoscale responses of heterogeneous explosives under shock loading were investigated by using a three-dimensional discrete element method. Numerical simulations without chemical reaction were conducted to explore the hot spot mechanisms in plastic bonded explosives and explosives containing voids of different shape and different size. The simulation results indicate that for shocked PBX explosives hot spots mostly locate near the interface between HMX crystals and binder, the temperature rise of HMX crystals is lower than that of the binder, and the surrounding parts of HMX crystals have higher temperature rise than the inner parts. For explosives containing a void, temperature of hot spot induced by the collapse of a big void is higher than that induced by the collapse of a small void, and temperature of hot spot induced by the collapse of a spherical void is higher than that induced by the collapse of a cubic void.