We prepared SnOx modified ultra-small size Pt catalyst. The catalyst shows good stability under ORR reaction conditions, especially after 40,000 cycles in the potential range of 0.6 ~ 1.2 V, the mass activity decreases by 11% and the electrochemical active area decreases by 19%. Under the hydrogen/oxygen conditions of the fuel cell, the cathode catalyst Pt loading is 0.05 mgPt cm -2 , the power density is 1.04 W cm -2 , and it maintains 91% after 10,000 cycles at