The　nickel-based　GH4169　superalloy　is　widely　used　in　the　aerospace　field,　which　has　desirable　oxidation　resistance　and　strength　in　extreme　environments.　However,　the　size　effect　and　underlying　microstructural　mechanism　in　the　cyclic　deformation　of　the　GH4169　sheet　are　still　not　fully　elucidated,　which　affects　the　forming　accuracy　precision　of　thin-walled　components.　To　this　end,　the　cyclic　mechanical　properties　and　microstructural　evolution　of　the　GH4169　sheets　with　different　thicknesses　and　grain　sizes　were　systematically　investigated　via　cyclic　shearing　tests.　The　superalloy　sheet　exhibits　obvious　early　re-yielding,　instantaneous　softening　and　permanent　softening　during　the　cyclic　deformation　and　these　cyclic　deformation　behaviors　are　obviously　affected　by　size　effect.　To　rationalize　the　cyclic　mechanical　responses　and　size　effect,　transmission　electron　microscopy　(TEM)　and　electron　backscatter　diffraction　(EBSD)　tests　were　conducted.　The　results　indicated　that　the　dislocation　slip　patterns　are　principally　planar　array　slip　and　cross　slip　in　the　cyclic　shearing　deformation.　Meanwhile,　the　annihilation　of　unstable　dislocation　and　the　presence　of　carbides　led　to　the　instantaneous　softening.　Moreover,　the　change　of　loading　direction,　the　reduction　of　texture　strength,　the　proportion　of　low-angle　grain　boundary　(LAGB),　and　geometrically　necessary　dislocation　(GND)　density　together　result　in　the　occurrence　of　permanent　softening.　Based　on　the　comparative　analysis　of　the　microstructure　evolution　of　superalloy　sheets　with　different　size　factors,　the　underlying　mechanism　of　size　effect　on　cyclic　deformation　was　clarified.　The　findings　in　the　research　combine　the　cyclic　mechanical　response　and　microstructure　evolution　closely　in　the　cyclic　deformation　of　superalloy　sheets　and　deepen　the　understanding　of　size　effect　under　complex　loading　paths.