Exploiting noble-metal free cocatalysts is of great importance for water splitting via solar energy. Molybdenum disulfide (MoS2) has been identified as a promising non-precious-metal cocatalyst to replace Pt. Here, two facile synthetic routes including a hydrothermal process and a liquid exfoliation strategy were adopted and screened for finely controlled synthesis of MoS2 QDs cocatalysts and their application in the visible-light photocatalytic hydrogen production. It was confirmed that the MoS2 QDs-L (L is the abbreviation of liquid exfoliation method) as cocatalyst can remarkably enhance the photocatalytic hydrogen activity of CdS under visible-light irradiation. Notably, with lactic acid as a sacrificial agent, the MoS2 QDs-L/CdS photocatalyst achieved an optimal hydrogen production activity with a rate of 1032.1 mu mol h(-1), which was 2.7 times more effective than that of the corresponding bulk MoS2/CdS (383.5 mu mol h(-1)) and 15.4 times more effective than that of the bare commercial CdS (66.9 mu mol h(-1)). In the meantime, the MoS2 QDs-L/CdS exhibited a good stability of in the cyclic runs for the photocatalytic hydrogen production. Impressively, it was found that a higher electrocatalytic activity of MoS2 QDs-L/CdS is directly consistent with a higher photocatalytic activity of MoS2 QDs-L/CdS during the hydrogen production. These findings will open opportunities for developing low-cost, high efficiency and stable photocatalyst that will find potential applications both in environmental protection and in renewable energy areas.