The N-ZnO/g-C3N4 composites prepared by high temperature calcination exhibited excellent performance in both the photocatalytic H-2 evolution and photocatalytic degradation of Methylene blue (MB). It can be seen that the absorption range of ZnO extends from ultraviolet light to UV-visible light after N dopant. The combination with g-C3N4 further enhances the absorption range of N-ZnO, thereby increasing the utilization of light. A Z-scheme photocatalytic system mechanism of N-ZnO/g-C3N4 has been proposed for the enhanced H-2 evolution and photocatalytic degradation rate. The proper bands position of N-ZnO facilitates the formation of Z-scheme mechanism. The electrons on CB of N-ZnO would migrate to VB of g-C3N4, which can effectively prevent the recombination of electrons and holes. The generation of electrons in CB of g-C3N4 and accumulation of holes in VB of N-ZnO can improve the photocatalytic efficiency.