In　this　paper,　a　supercell　modeling　of　secondary　orientation　was　established　using　90　cubic　mosaic　units　made　up　of　gamma＇　phase　embedded　in　gamma　matrix,　in　accordance　with　an　actual　structure　of　Ni-based　single　crystal　superalloys　(NSCS).　The　effects　of　secondary　orientation　on　the　deformation　behavior　and　microstructure　evolution　of　NSCS　under　uniaxial　tensile　were　studied　by　a　three-dimensional　molecular　dynamics　(MD)　simulation.　Simulation　results　showed　that　secondary　orientation　had　a　significant　effect　on　mechanical　properties　of　NSCS,　that　is,　a　big　fluctuation　was　found　in　tensile　strength　which　dropped　down　almost　50%　from　a　peak　(corresponding　to　the　secondary　orientations　of　18　degrees　and　45　degrees)　to　a　trough　(those　of　34　degrees　and　63　degrees).　Mechanisms　of　secondary　orientation　affecting　the　deformation　behavior　were　further　discussed　systematically.　The　deformation　of　NSCS　under　uniaxial　tensile　was　a　process　tending　towards　amorphization　of　microstructure,　together　with　the　dislocation　formation,　merging　and　break-up.　On　a　micro　viewpoint,　this　work　for　us　will　be　useful　to　apprehend　the　tensile　deformation　conduct　of　NSCS.