In　order　to　study　the　effect　of　different　crystal　orientation　on　femtosecond　laser　processing　of　silicon.　A　515　nm　green　high　power　femtosecond　laser　was　used　to　ablate　Si(111)　and　Si(100)　by　changing　the　average　laser　power　and　scanning　times.　The　difference　of　groove　ablation　depth　and　groove　bottom　roughness　between　the　two　crystal　planes　was　compared.　Electron　backscatter　diffraction　(EBSD)　was　used　to　study　the　micro　behavior　of　different　crystal　faces　in　femtosecond　laser　ablation.　The　amorphization　threshold　and　ablation　threshold　of　different　crystal　faces　were　compared,　and　meanwhile　the　amorphization　ability　and　recrystallization　ability　of　different　crystal　faces　were　compared.　With　the　increase　of　average　laser　power　and　scanning　times,　the　groove　formed　by　laser　ablation　becomes　deeper　and　deeper.　Under　the　same　conditions,　the　groove　depth　of　Si(111)　is　greater　than　that　of　Si(100),　and　the　groove　bottom　roughness　of　Si(111)　is　greater　than　that　of　Si(100).　When　the　groove　depth　reaches　300　μm,　the　groove　depth　of　Si(111)　is　about　20　μm　deeper　than　that　of　Si(100),　the　roughness　of　Si(111)　is　about　4　μm　high　than　that　of　Si(100).　The　amorphous　thresholds　of　the　two　silicon　planes　were　obtained　by　EBSD　technique,　which　were　approximately　0.16　J/cm2.　At　the　same　amorphization　threshold,　the　degree　of　amorphization　of　Si(111)　is　greater　than　that　of　Si(100).　It　is　observed　that　the　laser　absorptivity　of　Si(111)　is　higher　than　that　of　the　Si(100)　with　less　laser　scanning　times.　The　crystal　orientation　not　only　affects　the　microstructure　of　silicon　under　the　action　of　femtosecond　laser　multi　pulse,　but　also　affects　the　effect　of　femtosecond　laser　processing.　When　the　processing　parameters　are　the　same,　the　ablation　depth　of　Si(111)　is　significantly　greater　than　that　of　Si(100),　because　the　amorphous　ability　of　Si(111)　is　stronger　than　that　of　Si(100),　which　leads　to　more　laser　energy　absorption　and　higher　material　removal　efficiency　of　Si(111).　©　2021,　Chongqing　Wujiu　Periodicals　Press.　All　rights　reserved.