The pure molybdenum powder was consolidated to bulk material with the relative density of over 0.98 via high-pressure torsion (HPT) processing at 350 ℃. The deformation of particles and pores, the evolution of crystallite size and dislocation density, and the strengthening mechanism during HPT processing were analyzed through scaning electron microscopy (SEM), X-ray diffraction (XRD) and the Vickers microhardness. The influence of applied pressure during HPT on the microstructure evolution, mechanical properties and thermal stability were discussed. The results show that the relative density and average microhardness of the HPT processed sample were improved obviously with the increasing applied pressure from 2.0 GPa to 3.0 GPa. Also, the crystallite size and microstrain experience a decrease and an increase with the increasing applied preassure which leads to the increase of dislocation density. In addition, the grain size in the HPT processed sample has a finite increase during the DSC processing, which indicates the thermal stability of HPT processed microstructure.