The invention belongs to the field of utilization of biomass energy, and particularly relates to a method for preparing phenol through catalytic pyrolysis of biomass under the combined action of phosphate and activated carbon. The method comprises the following steps: loading phosphate on biomass in an impregnation manner; and by taking the biomass impregnated with the phosphate as a raw material and activated carbon as a catalyst, mechanically mixing the both, performing flash pyrolysis under oxygen-free conditions at 280-450 DEG C, and condensing the pyrolysis gas to obtain a phenol-enriched liquid product, wherein both the phenol yield and the phenol purity in the liquid product are high. Besides, the activated carbon catalyst is stable in performance, and can be recycled after separation and recovery; and the solid coke product containing the phosphate can be activated for preparation of the activated carbon for catalyzing the pyrolysis process.