CoO/g-CN hybrid catalyst is facilely prepared for application to photocatalytic H evolution from water splitting by the vacuum rotation-evaporation and thermal method. The physical and chemical properties of CoO/g-CN are determined by a series of characterization methods. The g-CN with 0.6 wt% Co loading exhibits superior photocatalytic hydrogen evolution activity with an H evolution amount of 23.25 mmol g after 5 h. The obtained 0.6 wt% CoO/g-CN can split water to generate 0.39 mmol g H without sacrificial agent and noble metal, while the pure g-CN is inactive under the same reaction conditions. The remarkable enhancement of photocatalytic H evolution activity of CoO/g-CN composites is mainly ascribed to the effective separation of electron-hole pairs and charge transfer. The work creates new opportunities for the design of low-cost g-CN-based photocatalysts with high photocatalytic H evolution activity from overall water splitting.