The selectivity and stability of Pt?based catalysts can be improved by adjusting the active phase by adding additives. The active phase of Pt?based catalyst was regulated by changing n(Ga)/n(Pt) with Ga as an additive and characterized by BET, FT-IR, TG, H₂-TPR, etc. The n(Ga)/n(Pt) of the active phase was optimized under the reaction temperature of 580 ℃, volume space velocity of 2 000 h^-1 and hydrogen?hydrocarbon ratio (volume ratio of hydrogen to propane) of 1. The results show that the Pt in the Pt7Ga/Al₂O₃ catalyst has the smallest particle size and the best dispersion.The Pt7Ga/Al₂O₃ catalyst has the best dehydrogenation performance, and the propylene selectivity of the reaction for 3 h was 90.98%, which was 3.01% higher than that with the PtSn/Al₂O₃ catalyst. The regulation of Ga can enhance the interaction force between Pt and Al₂O₃ support, lower the acidity of catalyst and the degree of graphitization of catalyst carbon deposition.