Efficient　methane　photooxidation　to　formic　acid　(HCOOH)　has　emerged　as　a　sustainable　approach　to　simultaneously　generate　value-added　chemicals　and　harness　renewable　energy.　However,　the　persistent　challenge　lies　in　achieving　a　high　yield　and　selectivity　for　HCOOH　formation,　primarily　due　to　the　complexities　associated　with　modulating　intermediate　conversion　and　desorption　after　methane　activation.　In　this　study,　we　employ　first-principles　calculations　as　a　comprehensive　guiding　tool　and　discover　that　by　precisely　controlling　the　O-2　activation　process　on　noble　metal　cocatalysts　and　the　adsorption　strength　of　carbon-containing　intermediates　on　metal　oxide　supports,　one　can　finely　tune　the　selectivity　of　methane　photooxidation　products.　Specifically,　a　bifunctional　catalyst　comprising　Pd　nanoparticles　and　monoclinic　WO3　(Pd/WO3)　would　possess　optimal　O-2　activation　kinetics　and　an　intermediate　oxidation/desorption　barrier,　thereby　promoting　HCOOH　formation.　As　evidenced　by　experiments,　the　Pd/WO3　catalyst　achieves　an　exceptional　HCOOH　yield　of　4.67　mmol　g(cat)(-1)　h(-1)　with　a　high　selectivity　of　62%　under　full-spectrum　light　irradiation　at　room　temperature　using　molecular　O-2.　Notably,　these　results　significantly　outperform　the　state-of-the-art　photocatalytic　systems　operated　under　identical　condition.