As the diffusion and migration of the deterrents affect the service life of gun propellants during the storage period， the molecular dynamics simulation （MD simulation） was applied to compare the diffusion rate of the small molecule dibutyl phthalate （DBP） and polyneopentyl glycol adipate （NA） in gun propellants. Meanwhile， the effect of nitroglycerin （NG） content on the diffusion of DBP and NA in double base gun propellants was explored and the diffusion mechanism was analyzed. The results indicate that the diffusivity of DBP and NA in nitrocellulose （NC） is equivalent at 5 ℃ and the diffusion coefficients are both in the order of 10^-12 m²∙s^-1. The diffusion coefficients of DBP and NA are 1.88×10^-11 m²∙s^-1 and 7.57×10^-12 m²∙s^-1 at 65 ℃， respectively. The diffusion coefficients of DBP and NA are 3.42×10^-11 m²∙s^-1 and 1.11×10^-11 m²∙s^-1 at 85 ℃， respectively. At the same temperature， the order of the diffusion coefficient of the deterrents is DBP>NA， which shows that NA has better anti-migration properties， which are more prominent at high temperatures. Owing to the high temperature， the peak value reduces， thus weakening interaction between DBP， NA and NC， meanwhile， the fractional free volume of system increases， which is conducive to the diffusion of DBP and NA. The diffusion capacity of DBP and NA increases with the increase of NG content. Adding NG weakens the interaction between DBP， NA and NC， so DBP and NA move more actively and the diffusion ability increases. The molecular dynamics simulation method is used to study the diffusion properties of the deterrents in gun propellants， which provides important theoretical guidance for predicting the life of gun propellants.