Single atomic metal (SAM) cocatalysis is a potential strategy to improve the performance of photocatalytic materials. However, the cocatalytic mechanism of SAM sites in different valence states is rarely reported. Herein, single atomic Pt²⁺/Pt⁰ active sites were anchored on Sb₂S₃ nanorods to synergistically improve the photoactivity for hydrogen production under simulated sunlight. Experimental results and density functional theory calculations indicated that the coexistence of single atomic Pt²⁺/Pt⁰ sites synergistically improves the broadband light harvesting and promotes the Sb₂S₃-to-Pt electron transfer following inhibited photoexciton recombination kinetics and enhanced H proton adsorption capacity, resulting higher and more durable photoactivity for hydrogen production. Therefore, the optimal Sb₂S₃-Pt_0.9‰ composite catalyst achieved remarkably enhanced hydrogen evolution rate of 1.37 mmol?g^-1?h^-1 (about 105-fold greater of that of Sb₂S₃ NRs) under faintly alkaline condition, and about 5.41% of apparent quantum yield (AQY_{700 nm}) was achieved, which shows obvious superiority in hydrogen production by contrasting with the reported Sb₂S₃-based photocatalysts and conventional semiconductor photocatalytic materials modified with noble metals. This study elucidate a well-defined mechanism of multisite cocatalysis for photoactivity improvement.