Thermal　stability　is　a　crucial　issue　for　engineering　application　of　tungsten,　especially　as　plasma　facing　material　in　future　fusion　reactor.　Two　kinds　of　ODS-W　alloys　of　W-0.5Y2O3　(WY)　and　W-0.5Y2O3-0.25Ti　(WYT)　were　fabricated　by　ball　milling　and　spark　plasma　sintering　aiming　at　formation　of　oxide　dispersoids　with　different　crystallographic　structures.　Thermal　stability　of　both　ODS-W　alloys　was　evaluated　in　terms　of　microhardness　and　microstructure　evolution　during　isothermal　aging　at　1100　degrees　C.　Dispersoids　of　sesquioxide　Y2O3　were　identified　in　sintered　WY,　while　pyrochlore　Y2Ti2O7　with　finer　size　and　higher　number　density　were　developed　in　sintered　WYT,　resulting　in　higher　bending　strength　of　1020　MPa　and　microhardness　of　880　HV.　Compared　with　sesquioxide　Y2O3,　complex　dispersoids　of　pyrochlore　Y2Ti2O7　exhibited　much　better　coarsening　resistance　during　isothermal　aging　at　1100　degrees　C　up　to　100　h,　where　the　intracrystalline　and　GB　dispersoids　maintained　around　10　nm　and　30　nm,　respectively.　The　excellent　coarsening　resistance　of　complex　Y2Ti2O7　with　pyrochlore　structure　contributed　to　grain　refinement　and　improved　microstructure　stability　of　WYT　due　to　the　effect　of　Zener　drag.