Constructing　dual　sites　is　promising　to　break　scaling　relations　between　the　adsorption　energetics　of　reaction　intermediates　and　ultimately　improves　the　activity　and　selectivity　due　to　the　synergistic　effect.　However,　it　is　a　grand　challenge　to　precisely　form　a　dual-site　configuration　with　one　metal　site　adjacent　to　another　active　site.　Loading　single　atoms　onto　oxides　with　pre-introduction　of　surface　oxygen　vacancies　may　be　an　alternative　strategy　to　overcome　such　challenge.　Motivated　by　our　theoretical　calculations　that　the　dual　sites　formed　by　single　Cu　atoms　and　unsaturated　Ti　sites　on　TiO2　enables　a　higher　activity　towards　hydrogen　evolution　from　water　splitting　than　corresponding　single　site,　we　successfully　synthesized　a　Cu-1-Ti　dual-site　catalyst　by　depositing　Cu　single　atoms　on　TiO2　nanoparticles　with　abundant　surface　oxygen　vacancies.　The　designed　target　catalyst　significantly　outperforms　the　benchmark　Pt　nanoparticle　decorated　TiO2　with　a　high　and　stable　activity　towards　photocatalytic　hydrogen　production.