Nanocrystal sintering is a key method to obtain a fully dense compact with fine grain size, and it is very necessary to improve its mechanical properties through grain boundary strengthening. A one-step plasma synthesis strategy was developed to synthesize molybdenum nanopowders with ammonium molybdate as the precursor. The reaction can be completed in an ultra-fast manner within a few seconds. The resulting product has a single crystal structure and a quasi-spherical shape with a size of about 30 nm. The sintering behavior of Mo nanoparticles was further studied through isothermal and non-isothermal processes, and the results showed that Mo compacts experienced different grain growth and microstructure evolution at different sintering stages. A completely dense Mo compact (99.13%) was obtained at a relatively low temperature of 1500°C, and the grain growth was well suppressed, about 7μm. The kinetic analysis showed that the surface diffusion with low activation energy was nanometer size The reason for the high sintering activity. Powder at low temperature.