The　effect　of　solid　solution　of　nitrogen　element　on　crystal　grain　of　developed　austenitic　manganese　steel　with　high　thermal　conductivity　is　studied.　The　results　indicate　that　the　crystal　grain　of　manganese　steel　in　casting　is　affected　by　the　nitrogen　in　the　interface　between　crystal　and　liquid　steel　as　surfactant,　and　the　diffusion　of　relevant　atoms　are　hindered　by　nitrogen,　so　that　free　energy　of　critical　nucleation　will　be　increased,　homogeneous　nucleation　rate　of　crystal　raised　and　growing　velocity　of　crystal　lowered,　and　crystal　grain　will　be　refined　finally　in　steel　casting.　The　effect　degree　of　nitrogen　on　crystal　grain　of　steel　is　affected　by　nitrogen　content.　During　heat　treatment,　because　of　covalent　bond　between　nitrogen　and　iron　and　manganese　atoms,　the　diffusion　of　iron　and　manganese　atoms　will　be　hindered　due　to　the　existence　of　nitrogen　at　boundary　of　crystal　or　the　attachment　of　nitrogen　on　the　face　of　crystal,　so　that　growing　velocity　of　crystal　will　be　lowered　and　the　crystal　grain　of　steel　can　be　controlled.　The　new　kind　of　austenitic　manganese　steel　decreases　the　content　of　manganese　below　8%,　the　content　of　carbon　to　about　1%,　and　the　content　of　nitrogen　about　0.07%,　the　crystal　grain　grade　of　developed　steel　reaches　the　class　4,　and　its　mechanical　properties　meet　those　required　by　standard　manganese　steel　Mn13.　©,　2014,　Science　Press.　All　right　reserved.