The design and development of noble metal-free, low-cost and stable co-catalyst are of great significance to the practical application of photocatalysts. In this work, the Mo incorporated Ni nanosheets (MoNi NSs) are successfully prepared and loaded onto g-CN via a simple and controllable method. The controlled loading of MoNi NSs with an optimal Mo intake can greatly enhance the photocatalytic H-evolution property of g-CN (MoNi/CN5). Specifically, the MoNi/CN5 exhibits the highest photocatalytic H-evolution rate of 273.2 μmol h (5464 μmol h g), which is the highest rate under one-solar light in the g-CN systems coupled with noble-metal-free co-catalysts. The greatly enhanced photocatalytic H-evolution activity of MoNi/g-CN is attributed to the role of MoNi as an outstanding co-catalyst to promote the carriers’ separation and transfer, and accelerate the surface H evolution reaction (HER).