The present invention discloses a preparation method of a secondary fuel cell air electrode catalyst based on a biomass. After a biomass is washed with water to remove impurities, the biomass is pyrolyzed in air, the obtained material and ammonium chloride are mixed in the argon in proportion to achieve doping and pre forming of nitrogen, the mixture is subjected to hydro-thermal treatment in a reaction still to improve the specific surface area of the material, and the mixture is further subjected to calcinations in the argon to improve the electrical conductivity and the activity of the material. The secondary fuel cell air electrode catalyst has a good electro-catalytic property.