The invention discloses a preparation method of a magnetic composite photocatalyst MnZn<1-x>Fe2O4/beta-Bi2O3/BiVO4, and belongs to the field of inorganic catalytic materials. The preparation methodcomprises the steps that MnZn<1-x>Fe2O4 is prepared through a hydrothermal method firstly, then a MnZn<1-x>Fe2O4/BiVO4 magnetic composite photocatalyst is prepared through a co-precipitation and roasting method, and then the magnetic composite photocatalyst MnZn<1-x>Fe2O4/beta-Bi2O3/BiVO4 is prepared through a precipitation and roasting method. According to the preparation method, the preparation technology is simple, the cost of adopted equipment is low, and energy consumption is less; prepared MnZn<1-x>Fe2O4/beta-Bi2O3/BiVO4 is high in specific surface area, high in stability and high in photocatalytic activity, under irradiation of a simulated sunlight xenon lamp, 0.1 g of a prepared composite photocatalytic material degrades 50 mL of a Rhodamine B solution with the concentration being 10 mg/L, after irradiation for 3 h, the degradation rate reaches 92.8%, after three times of reuse, the recovery rate is 89.7% or above, and after the three times of reuse, the degradation rate to the Rhodamine B solution still reaches 84.9% or above. A product prepared through the preparation method can be widely used in the field of photocatalytic degradation of organic pollutants.