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.