The invention relates to a preparation method of phenolic resin based foam carbon and belongs to the technical field of porous carbon material preparation. The preparation method disclosed by the invention comprises the steps: firstly taking loofah sponge and hydrogen peroxide to be evenly mixed, performing ultrasonic oscillation, utilizing a sodium hydroxide solution to adjust pH, then adding manganese acetate, stirring, standing, filtering, collecting filter residues, washing the filter residues by water until washed liquid is in a neutral state, collecting the washed filter residues, drying and collecting dry articles; pre-carbonizing the dry articles and collecting pre-carbonized articles; taking phenolic resin to be ball milled with polyaniline, collecting ball-milling articles, stirring and mixing the ball-milling articles, n-pentane, N,N-dimethyl formamide and acetone, collecting a stirred mixture, mixing the pre-carbonized articles with the stirred mixture, centrifugally separating, collecting low-layer precipitation to obtain a foam carbon precursor and finally carbonizing the foam carbon. The phenolic resin based foam carbon prepared by the preparation method disclosed by the invention has high porosity, easiness in whole structure control and further small harm to environment and production equipment.