Noble metal-free Ni-Mo-S nanoparticles modified graphitic C₃N₄ for efficient hydrogen evolution was successfully synthesized by means of a simple hydrothermal ion exchange process. This composite photocatalyst exhibits about 14 times higher photocatalytic activity of hydrogen production than that of the pure g-C₃N₄. Fluorescence analysis and electrochemical characterization confirmed that molybdenum sulfide and nickel sulfide as catalyst significantly enhanced the transfer of electrons on g-C₃N₄ and resulted in the excellent synergistic effect in photocatalytic properties. The promoted charge separation was measured by means of the EIS, photocurrent and transient fluorescence. A series of studies shown that the Ni_xMo_1-xS₂ nanoparticles modified on the surface of graphitic C₃N₄ provided the more active sites and improved the efficiency of photo-generated charge separation with several characterizations such as SEM, XRD, XPS, element mapping, UV–vis DRS, Transient photocurrent and BET etc. and the results of which were in good agreement with each other. The composite photocatalyst g-C₃N₄/Ni_xMo_1-xS₂ has a greater specific surface area and pore volume compared to pure g-C₃N₄, which is more favorable for the adsorption of dye molecules, leading to enhance the composite photocatalytic activity consequently. The excited-electron recombination process were greatly modulated with the introduce Ni-Mo-S nanoparticles on the surface of g-C₃N₄ and the photostability was enhanced as well. In addition, a possible reaction mechanism over eosin Y-sensitized g-C₃N₄/Ni_xMo_1-xS₂ photocatalyst under visible light irradiation was proposed.