Employing visible light responsive semiconductor for photocatalytic hydrogen production by water splitting is an efficient way for utilizing renewable solar energy to solve the depletion of fossil fuel and environmental contamination. Herein, we report enhanced photocatalytic H2-production performance over CdS nanorod using cobalt-phosphate (Co-Pi) as a water oxdation cocatalyst. The optimal Co-Pi modified CdS nanocomposite photocatalyst with the Co-Pi content of 8.4 mol% has a superior visible light H2-production rate of 13.3mmolh−1g−1 with an apparent quantum efficiency of 24.3% at 420nm, which is even higher than that of 1wt% Pt-CdS (11.3mmolh−1g−1) under the same conditions. The enhanced visible-light photocatalytic H2 production activity was attributed to the hole trapping and collecting ability of Co-Pi cocatalyst, which could effectively suppress the recombination of photogenerated electron-hole pairs and increase the electron density for hydrogen production. This work shows a possibility of using earth-abundant Co-Pi as cocatalyst for enhancing photocatalytic H2 production.