The invention discloses a catalyst for preparing ethylene and propylene through dehydrogenation of low-carbon alkane. According to the catalyst, magnesium-aluminum hydrotalcite is used as a carrier, platinum is used as an active component, tin is used as an addition agent, the loading capacity of the platinum is 0.1-3wt%, and the loading capacity of the tin is 0.01-3wt%. The catalyst is obtained through loading the platinum and the tin by the magnesium-aluminum hydrotalcite by an ion exchange method. Compared with the catalyst prepared by a conventional impregnation method, the prepared catalyst disclosed by the invention is simple in preparation technology, has high platinum dispersity, is good in stability in a direct dehydrogenation reaction of alkane, and is good in activity and high in selectivity, and besides, the catalyst can still maintain good catalytic activity after regeneration.