Mo nanopowders and micropowders were subjected to conventional sintering and microwave sintering at different sintering temperatures and sintering times, respectively. The results showed that with the increase of sintering temperature, the increase rate of relative density and hardness first increased rapidly and then slowed down. The relative density quickly reached 95%, and then there was a small change. Mo nanopowders with a relative density of 98.03% and an average grain size of 3.6 μm were prepared by microwave sintering at 1873 K for 30 minutes. According to the analysis of sintering kinetics, its densification is attributed to the combination of volume diffusion and grain boundary diffusion mechanisms. The calculated activation energy for sintering of Mo nanopowders is 203.65 kJ/mol, which is significantly lower than that of conventional sintering, indicating that microwave sintering is beneficial to enhancing the atom diffusion and densification of the powder. The results confirmed that microwave sintering is a promising method for economically preparing high-performance molybdenum.