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Thermodynamic calculation, ab initio molecular dynamics (AIMD) and vacuum decomposition experiments were performed to study the volatilization behaviors of Mo and S from molybdenite concentrate by vacuum decomposition. In thermodynamic calculation, starting decomposition temperatures of reactions were calculated, and saturated vapor pressures of Mo, S and MoS2 were also analyzed. In AIMD, geometries of the Sn(n≤8), Mom(m≤8) and MomSn(m+n≤8) clusters have been optimized using density functional theory (DFT) with generalized gradient approximation (GGA). And these clusters were simulated in DFT with Cambridge Sequential Total Energy Package (CASTEP) code of Material Studio software. Structures and stabilities of these clusters before and after molecular dynamics simulations were discussed, and diffusion coefficients were also calculated. In vacuum decomposition experiments, relationship between heat preservation time and volatilization rate of Mo and S was obtained, while the constant temperature and chamber pressure were 1823 K and 5-35 Pa, respectively. Above all, both the theoretical and experimental results showed that volatilization behaviors of Mo and S during vacuum decomposition process of molybdenite concentrate were as follows: Mo could partly evaporate into the condensate in the form of clusters, and S could easily evaporate into the condensate.