The invention relates to a preparation method and a purpose of a Zn mixed SnO2 ball with a mesoporous micro/nano hierarchical structure. The preparation method comprises the following steps: adding stannic chloride pentahydrate, zinc gluconate, sodium hydroxide and urea in a mixed solution of water and ethylenediamine, then reacting at the temperature of 170 to 200 DEG C, and finally washing and drying sequentially, and calcining for 30 to 60 minutes at the temperature of 300 to 500 DEG C to obtain the Zn mixed SnO2 ball with the mesoporous micro/nano hierarchical structure, wherein the mole ratio of stannic chloride pentahydrate, zinc gluconate, sodium hydroxide and urea is (1:2:12:2) to (1:2:12:6), the volume ratio of water and ethylenediamine is (2:1) to (1:2), and the reaction time is 4 to 24 hours. The preparation method has the characteristics of simplicity in operation, low cost, high purity of the product and the like. Through the invention, the photoelectric conversion efficiency of a DSSC (Dye Sensitized Solar Cell) is improved. In the preparation method, only heating and filtering in the traditional chemical industry are adopted, thereby facilitating the large-scale industrial production.