The invention discloses a method for preparing an activated carbon fiber membrane loaded ZnO photocatalyst. The method comprises the following steps: dissolving a precursor and a template agent into a solvent so as to obtain quenching liquid; performing thermally induced phase separation on the quenching liquid at the temperature of -50 to 0 DEG C so as to obtain a template/ZnAc composite fiber membrane; hydrolyzing the template/ZnAc composite fiber membrane in an ethanol solution of sodium hydroxide so as to obtain a template/Zn(OH)2 composite fiber membrane; activating the template/Zn(OH)2 composite fiber membrane in an aqueous solution of ammonium chloride, carbonizing at the temperature of 400-500 DEG C, thereby obtaining the activated carbon fiber membrane loaded ZnO photocatalyst. According to the method disclosed by the invention, low-price cellulose acetate serves as a raw material, an in-situ loading manner is adopted, and in-situ loading of ZnO on activated carbon fibers is realized. The preparation cost of the catalyst is reduced, and the loading capacity of ZnO is improved. Meanwhile, the activated carbon fibers prepared by in-situ preparation are on a nanoscale, the specific surface area is large, the adsorptive property of organic pollutants is greatly improved, and the photocatalytic activity is further improved.