Element　doping　has　been　extensively　employed　to　modulate　the　physicochemical　properties　of　semiconductors.　In　this　work,　Se-doped　CdS　quantum　dots　(QDs)　with　varied　Se　doping　level　are　fabricated　via　a　solvothermal　procedure.　Due　to　the　introduction　of　Se,　the　Fermi　level　position　of　CdS　is　elevated　to　a　higher　position,　leading　to　the　effective　capture　of　photogenerated　electrons　by　the　trapping　sites,　which　greatly　inhibits　the　recombination　of　electron-hole　pairs　and　thus　prolong　the　charge　carriers＇　lifetime.　Furthermore,　due　to　the　introduction　of　Se,　the　density　of　charge　carriers　in　CdS　is　significantly　enhanced,　which　is　conducive　to　the　production　of　more　photo-generated　electrons　and　holes.　It　is　because　of　the　two　favorable　factors　that　the　photocatalytic　performance　of　the　resultant　CdS0.9Se0.1　QDs　is　greatly　improved　with　a　remarkable　hydrogen　evolution　rate　of　29.12　mmol　h(-1)　g(-1)　under　simulated　solar　irradiation　(320-780　nm)　without　any　co-catalysts,　which　is　23.5　times　that　of　the　pristine　CdS　QDs　under　the　same　conditions.　Moreover,　the　apparent　quantum　efficiency　(AQE)　over　CdS0.9Se0.1　QDs　reaches　27.1%　at　400　nm　without　co-catalyst　addition.　This　work　confirms　the　feasibility　of　suppressing　the　recombination　of　electron-hole　pairs　by　adjusting　the　capture　level　with　impurity　doping　for　exploring　highly　efficient　photocatalysts.