The invention relates to a nano catalyst for preparing propylene by oxidative dehydrogenation of propane, which belongs to the technical field of chemical industry, and is a novel nano catalyst for preparing propylene by oxidative dehydrogenation of propane with nano mesoporous inorganic materials with large specific surface area as catalytic carriers and transition metal oxides as active components. Because the activity of propylene is higher than that of propane, propylene is easy to be further oxidized in the existing catalyst system, which leads to a great decrease in propylene selectivity. The catalyst carrier of the invention is SBA series pure silicon mesoporous molecular sieve, which has a regular two-dimensional or three-dimensional nano-pore structure with a pore size of 5-30 nanometers. This molecular sieve can be impregnated with active component transition metal oxide or its mixed oxide to prepare propylene catalyst with propylene yield as high as ~ 32%. In that present invention, if the modify catalyst is doped with common metal oxide,