Casing　shear　deformation　has　been　a　serious　issue　to　be　resolved　during　multistage　fracturing　in　shale　gas　horizontal　wells　in　the　world,　which　significantly　increased　the　well　stimulation　cost　and　reduced　the　production　capacity.　Fault　slipping　was　identified　as　a　significant　cause　and　not　easy　to　control.　A　new　device　of　bypass　cementing　device,　along　with　the　indispensable　accessories,　was　proposed　and　designed.　The　local　pressure　loss　of　the　device　was　calculated　to　analyze　the　compatibility　of　geometric　dimensions　between　the　wellbore　and　device,　and　the　device　structure　parameters　of　the　tools　were　optimized.　A　matched　application　process　that　was　able　to　make　the　slurry　bypassing　nature　fractures　developed　zone　was　established.　Then　a　series　of　corresponding　numerical　models　of　the　device　were　developed　and　to　simulate　the　variation　of　inner　diameter　in　the　casing　deformed　part　using　the　shell-to-solid　coupling　method,　and　the　shear　deformation　degrees　before　and　after　using　the　new　device　were　compared.　Simulation　results　showed　that　after　using　the　bypass　cementing　device,　the　reduction　of　casing　inner　diameter　after　fault　slipping　was　reduced　by　about　63.75%-75.6%,　which　could　effectively　protect　the　casing　integrity.　The　method　in　this　study　supplied　an　important　solution　for　dealing　with　the　problem　of　casing　shear　deformation　caused　by　fault　slipping　induced　by　multistage　fracturing　in　shale　gas　horizontal　wells.