Abstract: In recent years, photocatalytic N₂ reduction for ammonia synthesis at room temperature and atmospheric pressure has gradually become a research hotspot, exhibiting extremely high development potential. However, the low photogenerated charge separation efficiency and the lack of effective active sites seriously constrain the reaction efficiencies of semiconductor photocatalysts for N₂ reduction of ammonia synthesis. Therefore, the rational design of catalytic materials is the key to enhance the photocatalytic N₂ reduction reaction of ammonia synthesis. Transition metal Ru as the active center not only accelerates the adsorption and activation of N₂ molecules, but also has good selectivity for N₂ reduction. Moreover, the interaction between the metal and the support can effectively regulate the electronic structure of the active site, accelerate the photogenerated electron transfer, and significantly enhance the photocatalytic activity. Based on this, this review systematically investigates the Ru co-semiconductors to realize efficient photocatalytic N₂ reduction for ammonia synthesis, and introduces its basic principles. Specifically, the Ru co-semiconductor photocatalytic material systems are introduced, such as TiO₂-based, g-C₃N₄-based, and metal oxide materials, including the design of catalysts, crystal structures, and other characteristics. In addition, the modification strategies of photocatalytic N₂ reduction ammonia synthesis materials are also presented, including loading/doping, defect engineering, construction of heterojunctions, and crystal surface modulation. Furthermore, the progress and shortcomings of the application of Ru co-semiconductors in these processes are summarized and comprehensively discussed, and the future outlook of Ru co-semiconductors in photocatalytic N₂ reduction ammonia synthesis applications is proposed.