The effect of temperature on the crystallization of cyclotetramethylene tetranitramine(HMX) in dimethylsulfoxide(DMSO) solvent was investigated by molecular dynamics simulation. The diffusion coefficients of DMSO and HMX and binding energy between HMX and DMSO were calculated in 278-378 K. The process of nucleus formation of HMX was simulated at 298 K. The results show that the interaction force between HMX and DMSO is ascribed to the van der Waals′force and electrostatic force. The HMX molecular nucleation most easily takes place at 358 K.The nucleation makes the diffusion coefficient of HMX decrease.