The effect of crystal modifier 2,2',4,4',6,6'-hexanitrostillbene(HNS) on the reinforcement of crystalline 1,3,5-trinitrotoluene (TNT) was investigated by molecular simulation. The intermolecular interactions between HNS and TNT were revealed by quantum chemistry calculations in detail, strong attractive forces were found between HNS and TNT. The solid interface models of TNT/HNS along three crystalline directions were studied, the distance between HNS molecule and TNT system was narrowed after optimization; the mechanical properties were calculated, showing the mechanism of the reinforcement.