The invention belongs to the technical field of environmental catalytic materials, and more particularly relates to a porous nano manganese oxide catalyst and preparation and application thereof. Manganese salt and amino acid are mixed and dissolved in a solvent, then the temperature is raised to reach the ignition point of the amino acid, a combustion reaction occurs, a product is washed after the reaction is completed, and the porous nano manganese oxide catalyst is obtained after solid-liquid separation. When manganic oxide prepared by the method is applied to catalytic combustion of volatile organic compounds, the manganic oxide has the advantages of higher specific surface area, uniform pore size distribution, high catalytic activity, strong stability, excellent water resistance and the like. The porous nano manganese oxide catalyst has high combustion product selectivity, no secondary pollution, environmental friendliness, low cost and easy industrial production.