A novel MoS2 quantum dot (QD) decorated g-C3N4 (MoS2-QDs/CN) heterostructured photocatalyst has been synthesized via a simple wetness impregnation method. The as-prepared MoS2-QDs/CN composite exhibited strong absorption in the visible light region. Its photocatalytic activity on hydrogen evolution was evaluated by splitting water under visible light irradiation (lambda > 420 nm). The highest H-2 yield of 19.66 mu mol h(-1) was achieved on 50 mg 1 wt% MoS2-QDs/CN photocatalyst (loaded with 1 wt% Pt), which was 6.6 and 1.84 times those on pure g-C3N4 and 1 wt% Pt loaded g-C3N4, respectively.