The invention discloses a method for preparing a phosphate-doped polybenzimidazole membrane electrode for a fuel cell. On the one hand, 4,4'-oxybis(benzoic acid) and 3,3',4,4'-biphenyltetramine serve as monomers to prepare poly[2,2'-(p-oxy- diphenylene)-5-5'-bisbenzimidazole], the poly[2,2'-(p-oxy-diphenylene)-5-5'-bisbenzimidazole] is cast to form a membrane, and the membrane is doped with phosphate to prepare an electrolyte membrane with good mechanical strength; on the other hand, in the process of preparing a phosphate-doped gas diffusion electrode, poly-[2,2'-(m-phenylene)-5,5'-bisbenzimidazole] is prepared into the gas diffusion electrode in the presence of a platinum / carbon catalyst, the gas diffusion electrode is doped with phosphate, the components are uniformly distributed, strong-volatility acid is not used in the process, and a process of mixing solid materials does not exist. The membrane electrode prepared by the method can be used for hydrogen-oxygen fuel cell power generation under the conditions that the temperature is higher than 100 DEG C and the humidification is not carried out. The open-circuit voltage is 0.845V, and the maximum power density is 191mW / cm<2> (560mA / cm<2>, 0.34V) under the conditions that the temperature of the fuel cell is 150DEG C and the humidification is not carried out. The preparation method has the advantages of controllable conditions in the technological process and good repeatability of the process.