Casing　deformation　has　been　found　to　be　a　very　significant　issue　in　the　development　process　of　shale　gas　in　China.　The　rate　of　casing　deformation　is　34.34%　(34　wells　of　101),　and　statistical　data　show　that　it　decreased　the　test　output　of　wells　by　approximately　30%.　Based　on　investigation　and　analysis　of　the　engineering　and　geological　conditions　of　25　wells,　12　of　which　have　casing　deformations,　both　physical　models　and　finite　element　models　were　established.　Furthermore,　the　effects　of　fracturing　pressure,　geostress,　anisotropy,　lithologic　interface,　temperature　variation,　and　cement　void　were　analyzed.　The　results　show　the　following.　a)　When　the　casing　deformation　points　appear　far　away　from　point　A　(the　landing　point,　which　is　the　starting　point　of　the　horizontal　segment),　the　influence　of　the　lithologic　interface　on　casing　stress　plays　a　decisive　role　under　the　combined　effect　of　internal　and　external　pressures　when　the　cement　sheath　is　completed.　b)　Under　the　same　conditions,　but　when　the　casing　is　in　contact　with　the　borehole　wall　near　the　bottom　because　of　gravity,　a　narrow　fluid　retention　space　was　formed,　leading　to　cementing　sheath　voids.　The　effect　of　cement　void　pressure　reduction　is　the　main　reason　behind　the　casing　deformation.　c)　When　casing　deformation　points　appear　near　point　A,　the　activation　of　the　weak　plane　in　the　beddings　during　fracturing　causes　the　casing　deformation.　The　stress　of　14　casing　deformation　points　was　calculated　according　to　actual　engineering　and　geological　conditions,　and　78.6%　of　the　results　were　consistent　with　field　measurements.