The invention belongs to the technical field of electrocatalysis, and in particular relates to an efficient biomass carbon electrochemical oxygen reduction catalyst and a preparation method and application thereof. By taking agaric as a biomass raw material, the biomass carbon-based catalyst with good hydrophilicity is prepared by acid-boiling the biomass raw material by means of a carbonizing mode combining pre-carbonization and full carbonization. By taking the fungi agaric which is low in price, easily available and environment-friendly as the raw material, the demand on equipment is relatively low in the preparation process, the preparation flow is short, and the preparation method is simple to operate. The preparation method is environment-friendly in preparation process, free of waste discharge and quite beneficial to scale production, and has wide industrial application prospect.