The influences of temperature, content of nitroglycerin(NG), structure of diisocyanate on the diffusion behaviors of NG in elastomeric polyurethane were investigated by the molecular dynamics method with COMPASS(Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies) force field. The mixed models of NG and different elastomeric polyurethane were also constructed and optimized. The mean square displacement of NG in mixtures was obtained by the molecular dynamics simulation of NPT(constant-temperature, constant-pressure ensemble) and NVT(constant-temperature, constant-volume ensemble). The diffusion coefficients were obtained by the Einstein equation. The results show that the order of magnitude of diffusion coefficients of NG in elastomeric polyurethane reaches 10^-8 cm²·s^-1, which is in agreement with experiment. The diffusion coefficients increase with the increasing of chain flexibility, and increase slowly when the temperature belows 308 K and then increase quickly. At meanwhile, the diffusion coefficients decrease slowly at first, and quickly when the content of NG exceeds 14%.