In order to realize the precisely pressing formation of heteromorphic grain with certain type of anti-overload high explosive, the author performed the mould structure design. Mating clearance design and stress checking, and obtained the heteromorphic grain mould that meets the requirement of dimensions. After the study of process parameters on the forming quality of heteromorphic grain by pressing, the author acquired the optimal parameters. The result shows that, the designed heteromorphic grain mould meets the requirement of formation by pressing, and the optimal preheating temperature for the heteromorphic grain formation by pressing is 85℃±5℃, with the specific pressure of 1 800 kg/cm2 and the pressure hold time of 900 s. Under this condition, the pressed density of the high explosive can reach 2.044 g/cm3, Which equals to 98% of the theoretical density. And the precise pressing formation of heteromorphic grain is realized.