The　photocatalytic　CO2　reduction　reaction　is　a　sustainable　route　to　the　direct　conversion　of　greenhouse　gases　into　chemicals　without　additional　energy　consumption.　Given　the　vast　amount　of　greenhouse　gas,　numerous　efforts　have　been　devoted　to　developing　inorganic　photocatalysts,　e.g.,　titanium　dioxide　(TiO2),　due　to　their　stability,　low　cost,　and　environmentally　friendly　properties.　However,　a　more　efficient　TiO2　photocatalyst　without　noble　metals　is　highly　desirable　for　CO2　reduction,　and　it　is　both　difficult　and　urgent　to　produce　selectively　valuable　compounds.　Here,　a　novel　＂single-atom　site　at　the　atomic　step＂　strategy　is　developed　by　anchoring　a　single　tungsten　(W)　atom　site　with　oxygen-coordination　at　the　intrinsic　steps　of　classic　TiO2　nanoparticles.　The　composition　of　active　sites　for　CO2　reduction　can　be　controlled　by　tuning　the　additional　W5+　to　form　W5+-O-Ti3+　sites,　resulting　in　both　significant　CO2　reduction　efficiency　with　60.6　mu　mol　g(-)(1)　h(-)(1)　and　selectivity　for　methane　(CH4)　over　carbon　monoxide　(CO),　which　exceeds　those　of　pristine　TiO2　by　more　than　one　order　of　magnitude.　The　mechanism　relies　on　the　accurate　control　of　the　single-atom　sites　at　step　with　22.8%　coverage　of　surface　sites　and　the　subsequent　excellent　electron-hole　separation　along　with　the　favorable　adsorption-desorption　of　intermediates　at　the　sites.