Micro-occur　of　Si　wafer　under　rotating　disk　test　has　been　studied.　Four　kinds　of　Si　wafers,　including　as-cut　wafer,　chemically　eroded　wafer,　polished　wafer　and　etched　wafer,　were　tested　in　tap　water　for　8　hours　by　the　self-made　rotating　disk　test　rig.　Scanning　Electron　Microscope　(SEM),　Surface　Profilometer　and　Atomic　Force　Microscope　(AFM)　were　used　to　analyze　the　surface　properties　of　the　Si　wafer.　SEM　results　indicate　that　after　8　h　test　among　the　four　wafers,　as-cut　wafer　damaged　most　severely　because　its　lamina　layers　on　the　original　surface　vanished,　and　then　as-cut　wafer　for　its　keen　edge　were　smoothed,　the　polished　and　etched　ones　damaged　most　slightly　because　changes　can　hardly　be　found　after　test.　AFM　analysis　showed　that　after　8　h　test　the　surface　roughness　of　the　chemically　eroded　wafer　decreases　from　227.79　nm　Ra　to　173.31　nm　Ra　while　that　of　the　polished　one　increases　from　0.483　nm　to　3.455　nm.　Micro-occur　of　the　as-cut　wafer　was　observed　by　SEM　continuously　during　14　h　test　and　the　surface　roughness　decreased　from　0.3304　μm　Ra　to　0.1965　μm　Ra.　The　results　showed　that　the　degree　of　material　damage　of　Si　was　determined　by　the　dimension　of　its　micro　topography.