Semihydrogenation　is　a　crucial　industrial　process.　Noble　metals　such　as　Pd　have　been　extensively　studied　in　semihydrogenation　reactions,　owing　to　their　unique　catalytic　activity　toward　hydrogen　activation.　However,　the　overhydrogenation　of　alkenes　to　alkanes　often　happens　due　to　the　rather　strong　adsorption　of　alkenes　on　Pd　active　phases.　Herein,　we　demonstrate　that　the　incorporation　of　Pd　active　phases　as　single-atom　sites　in　perovskite　lattices　such　as　SrTiO3　can　greatly　alternate　the　electronic　structure　and　coordination　environment　of　Pd　active　phases　to　facilitate　the　desorption　of　alkenes　rather　than　further　hydrogenation.　Furthermore,　the　incorporated　Pd　sites　can　be　well　stabilized　without　sintering　by　a　strong　host-guest　interaction　with　SrTiO3　during　the　activation　of　H　species　in　hydrogenation　reactions.　As　a　result,　the　Pd　incorporated　SrTiO3　(Pd-SrTiO3)　exhibits　an　excellent　time-independent　selectivity　(＞99.9　%)　and　robust　durability　for　the　photocatalytic　semihydrogenation　of　phenylacetylene　to　styrene.　This　strategy　based　on　incorporation　of　active　phases　in　perovskite　lattices　will　have　broad　implications　in　the　development　of　high-performance　photocatalysts　for　selective　hydrogenation　reactions.