The invention discloses a preparation method for a bifunctional catalyst material for a lithium air battery. A cobalt nitride nanometer cubic-nitrogen doped carbon composite material is taken as an air electrode catalyst material. The preparation method comprises the following steps: dispersing cobalt salt and polyvinylpyrrolidone in methyl alcohol, thereby acquiring a dispersion solution; dissolving 2-methylimidazole in methyl alcohol, thereby acquiring another dispersion solution; mixing the two dispersion solutions, fully stirring for reacting, and then standing, purifying and washing, thereby acquiring a nanometer-scale metallic organic frame complex; performing fractional heat treatment on the complex at 300-400 DEG C, wherein the front fractional heat treatment is performed under inert atmosphere and the posterior fractional heat treatment is performed under the condition of introducing ammonia gas; and finally, acquiring the cobalt nitride nanometer cubic-nitrogen doped carbon composite material. When the material is applied to the catalyst for the lithium air battery, under the effects of high electronic transmission performance and stable catalytic performance of nitrides, the charging/discharging over-potential of the lithium air battery can be effectively reduced, the double-trip efficiency of the battery can be increased, and the circulating service life of the battery can be prolonged. The invention has the advantages of excellent catalytic performance of the catalyst material, simple and controllable preparation method, high operability and low production cost.