Casing　shear　deformation　has　become　a　prominent　problem　in　the　process　of　completion　in　shale　gas　wells.　It　was　believed　that　the　slide　of　strike-slip　fault　induced　by　multistage　fracturing　was　the　main　reason.　This　paper　presented　a　new　numerical　investigation　for　evaluating　the　casing　inner　diameter　after　strike-slip　fault　sliding　based　on　the　microseismic　data.　A　3D　finite　element　model,　considering　the　mechanical　anisotropy　of　shale　and　heat-fluid-solid　coupling　effect　during　multistage　fracturing,　was　developed　to　calculate　the　variation　of　casing　inner　diameter　after　fault　sliding　under　different　engineering　and　geological　conditions.　The　calculation　result　was　verified　by　comparison　with　the　measurement　result　of　the　multi-finger　caliper　survey.　Sensitivity　analysis　was　carried　out　and　the　results　showed　that　decreasing　the　sliding　distance,　maintaining　high　pressure,　increasing　the　casing　thickness,　and　increasing　the　elasticity　modulus　and　decreasing　the　Poisson　ratio　of　cement　sheath　were　beneficial　to　protect　the　casing　integrity.　Finally,　the　engineering　verification　demonstrated　that　the　numerical　method　has　an　accuracy　up　to　85.9%.　Numerical　model　in　this　study　was　expected　to　provide　a　better　understanding　of　casing　shear　deformation　and　an　evaluation　method　of　casing　inner　diameter　after　fault　sliding　during　multistage　fracturing　in　shale　gas　wells.