The invention relates to the field of catalysts, and discloses a propane dehydrogenation catalyst and a preparation method thereof and a method for preparing propylene through propane dehydrogenation.The propane dehydrogenation catalyst is prepared from a carrier, a main active components Pt, a metal additive Sn and a metal additive Na that are loaded on the carrier, wherein the carrier is a spherical double mesoporous illite composite carrier, the spherical double mesoporous illite composite carrier is prepared from illite, a mesoporous molecular sieve material with a one-dimensional hexagonal channel distribution structure, and a mesoporous molecular sieve material with a two-dimensional hexagonal channel distribution structure, the average particle size of the spherical double mesoporous illite composite carrier is 30-60 mum, the specific surface area thereof is 150-600m<2>/g, the pore volume thereof is 0.5-1.5mL/g, pore size is in bimodal distribution, and optimum apertures corresponding to bimodality are separately 2-8nm and 15-45nm. The propane dehydrogenation catalyst has high catalysis performance when being used in preparation of propylene through propane dehydrogenation,propane conversion rate is high, propylene selectivity is high, and the catalyst has high stability.