Nanostructure　surface　layer　in　316L　stainless　steel　sheet　(2.8　mm　thick)　was　induced　by　surface　mechanical　attrition　treatment　(SMAT).　The　thickness　of　nanostructure　surface　layer　increased　from　50　μm　to　150　μm　when　the　SMAT　time　increased　from　5　min　to　60　min.　The　mechanical　properties　of　the　SMAT　316L　stainless　steel　sheet　were　measured　and　the　tensile　fracture　surface　was　observed　by　SEM.　The　results　show　that　the　surface　layer　hardness　and　bulk　yield　strength　of　the　steel　sheet　increase　obviously　when　the　SMAT　time　is　5　minutes,　however,　no　such　increasing　is　observed　for　continuously　increasing　SMAT　time.　The　tensile　fracture　morphology　of　nanostructure　surface　layer　of　the　steel　sheet　SMAT　for　5　minutes　shows　elongated　dimples　and　increased　shear　lip　area.　The　plastic　deformation　capability　decreases　with　the　continuously　increasing　SMAT　time.