In this paper molecular dynamics (MD) simulation was applied to validate COMPASS force field for HMX. The crystal parameters of β-HMX crystal under atmospheric pressure and at seven different temperatures from 205 to 385 K were then calculated with MD simulation using NPT ensemble for β-HMX (4×2×3) primary simulation cell. Both linear coefficients of thermal expansion (CTEs) in the crystal a,b and c directions and volume CTEs were obtained using linear correlation method. These theoretical calculation results are in agreement with the previous experimental and theoretical data.