Abstract: A polymeric semiconductor material——g-C₃N₄ are currently studied by researchers as hot materials due to their excellent mechanic,optical and electrical properties.Base on analysis of structure and theoretical calculation,the reasons that g-C₃N₄ can be metal-free catalyst were discussed.The preparation and properites of different modified g-C₃N₄ including meso-porous g-C₃N₄,inorganic elements doped g-C₃N₄,metal-supported g-C₃N₄,g-C₃N₄/metal oxides composites and organnic compound modified g-C₃N₄ were summarized,and the mechanism,effect factors and research developments on the reaction of splitting water for hydrogen revolution catalyzed by above-mentioned modified g-C₃N₄ were focused on.The opinion on further studies are also presented in this article.