Nanocrystals　sintering　is　a　critical　way　to　achieve　full-densified　compact　with　fine　grain　size,　which　is　highly　desired　to　improve　its　mechanical　properties　by　grain　boundaries　strengthening.　In　this　work,　a　one-step　plasma　synthesis　strategy　was　developed　to　synthesize　Mo　nanopowder　using　ammonium　molybdate　as　precursor,　and　the　reaction　could　be　completed　by　an　ultrafast　way　in　several　seconds.　As　obtained　products　exhibit　single-crystalline　structure　and　quasi-spherical　shape　with　size　of　about　30　nm.　The　sintering　behavior　of　Mo　nanoparticles　was　further　investigated　by　isothermal　and　nonisothermal　processes,　and　the　results　reveal　that　Mo　compact　experiences　different　grain　growth　and　microstructure　evolution　at　different　sintering　stages.　Fully　densified　Mo　compact　(99.13%)　with　well　suppressed　grain　growth　of　about　7　mu　m　was　obtained　at　a　rather　low　temperature　of　1500　degrees　C,　and　kinetics　analysis　illustrates　that　the　surface　diffusion　with　low　activation　energy　is　responsible　for　the　high　sintering　activity　of　nanosized　powder　at　low　temperature.