In　situ　nanoindentation　was　employed　to　probe　the　mechanical　properties　of　individual　polycrystalline　titania　(TiO2)　microspheres.　The　force-displacement　curves　captured　by　a　hybrid　scanning　electron　microscope/scanning　probe　microscope　(SEM/SPM)　system　were　analyzed　based　on　Hertz＇s　theory　of　contact　mechanics.　However,　the　deformation　mechanisms　of　the　nano/microspheres　in　the　nanoindentation　tests　are　not　very　clear.　Finite　element　simulation　was　employed　to　investigate　the　deformation　of　spheres　at　the　nanoscale　under　the　pressure　of　an　AFM　tip.　Then　a　revised　method　for　the　calculation　of　Young＇s　modulus　of　the　microspheres　was　presented　based　on　the　deformation　mechanisms　of　the　spheres　and　Hertz＇s　theory.　Meanwhile,　a　new　force-displacement　curve　was　reproduced　by　finite　element　simulation　with　the　new　calculation,　and　it　was　compared　with　the　curve　obtained　by　the　nanoindentation　experiment.　The　results　of　the　comparison　show　that　utilization　of　this　revised　model　produces　more　accurate　results.　The　calculated　results　showed　that　Young＇s　modulus　of　a　polycrystalline　TiO2　microsphere　was　approximately　30%　larger　than　that　of　the　bulk　counterpart.