The overall water splitting efficiency is mainly restricted by the slow kinetics of oxygen evolution. Therefore, it is essential to develop active oxygen evolution catalysts. In this context, we designed and synthesized a tungsten oxide catalyst with oxygen vacancies for photocatalytic oxygen evolution, which exhibited a higher oxygen evolution rate of 683 μmol h−1 g−1 than that of pure WO3 (159 μmol h−1 g−1). Subsequent studies through transient absorption spectroscopy found that the oxygen vacancies can produce electron trapping states to inhibit the direct recombination of photogenerated carriers. Additionally, a Pt cocatalyst can promote electron trap states to participate in the reaction to improve the photocatalytic performance further. This work uses femtosecond transient absorption spectroscopy to explain the photocatalytic oxygen evolution mechanism of inorganic materials and provides new insights into the design of high‐efficiency water‐splitting catalysts. In photocatalytic oxygen evolution, some excited electrons can be trapped more easily to form trapped state electrons due to the presence of oxygen vacancies in Ov‐WO3‐600. This process can partially inhibit direct recombination and prolong the lifetime of photogenerated charges. In addition, photodeposited Pt can serve as an active site to capture the trapped state electrons to react with electron sacrificial agents.