SM2Fe17Nx　magnet　was　sintered　under　1　GPa　by　Spark　plasma　sintering(SPS)　technique.　The　microstructure　and　magnetic　properties　of　the　magnet　were　investigated.　The　results　show　that　the　density　of　the　magnets　is　obviously　improved　with　the　increase　of　sintering　temperature,　but　the　decomposition　of　Sm2Fe17Nx　into　SmN,　alpha-Fe　and　N-2　is　distinctly　promoted,　which　cause　the　rapid　decrease　of　the　coercivity.　On　the　basis　of　the　study　of　the　decomposition　mechanism,　it　is　found　that　the　decomposition　process　is　easy　to　nucleate,　but　difficult　to　grow.　The　microlite　or　amorphous　decomposition　phases　of　SmN　and　a-Fe　are　dispersed　and　fine.