Platinum oxide electrode, as an important part of hydrogen concentration monitoring sensor built in containment, made hydrogen sensor was at a bottleneck of due to its insufficient mechanical and electrocatalytic properties, which limited the overall localization process of AP1000 technology in China. In present study, platinum oxide film electrode was successfully prepared on platinum substrate by reactive magnetron sputtering, and the influence of different substrate temperature on the composition, morphology and electrocatalytic property of the film was investigated. The results show that platinum oxide film composed of PtO and PtO2 can be obtained in Ar/50%O2 sputtering atmosphere. As the temperature increases from room temperature (RT) to 200℃, the oxygen vacancies in the amorphous film are gradually repaired and convert to the crystalline state, and form a three-dimensional nano-dendritic and crack-free film, which shows increasing PtO2 ratio, increasing electrochemical active area (ECSA), and improved stability. When the temperature rising to 400℃, the film shows decreasing oxygen vacancies, increasing average grain size. Since PtO2 decomposes into PtO and Pt, and thus ECSA decreases, the stability and oxygen reduction activity of the films decreases gradually.