The invention discloses a biomass carbon catalyst and a preparation method and application thereof. The precursor of the catalyst comprises biomass and metal salts, wherein the biomass includes one or more of maize straw, corncob, rice straw, cotton straw, peanut straw, peanut shell, wheat hull, rice hull, wood, sawdust, bamboo wood and weed. Through controlling addition of metal salts in different amounts, adjusting impregnation concentration of the precursor and reaction ambient and carbonization and nitriding treatment temperatures, the biomass carbon catalyst with controllable and adjustable pore structure and specific surface area can be prepared. When used as a fuel battery cathode catalyst, the biomass carbon catalyst shows excellent oxygen reduction reaction activity and stability. The preparation process is simple in flow, short in period and free of environment, provides a novel high-value-added resource recycling way for waste biomass and has dual effects of biomass disposal and energy and power generation.