The invention provides a PdIn alloy catalyst. The PdIn alloy catalyst comprises a carrier and Pd metal loaded on the carrier, wherein the carrier is a nitrogen-doped porous carbon composite material with a plurality of pore channels, the nitrogen-doped porous carbon composite material comprises a nitrogen-doped porous carbon material, indium oxide and metal In which is exposed through the pore channels, the indium oxide is uniformly distributed in the nitrogen-doped porous carbon material, and corner positions of the Pd metal are selectively occupied by the metal In. The invention further provides a preparation method and application of the PdIn alloy catalyst.