In order to improve the acceleration ability of explosive detonation on metal fragments, the effects of the heat release of Al on the acceleration ability of metal fragment were discussed. By taking the cast heating PBX based on HMX as research object, the study on the effect of the heat release of Al metal on the ability to accelerate fragment was carried out though analysis of the warhead breaking and the loading process of metallic fragment based on the design of explosive formulas with different content of Al metal and testing of explosion heat according to GJB 772A-97. The results indicated that loading capacity of fragment is due to the matching ability between powering of heat release for Al and accelerating time including the time of explosive detonation, warhead broken time and loading time of detonation.