The invention discloses yttrium oxide dual-level nanospheres and a preparation method thereof. The yttrium oxide dual-level nanospheres are formed by aggregating yttrium oxide primary nanospheres andyttrium oxide secondary nanospheres, wherein the diameter of the secondary nanosphere is 20 to 150 nm, and the diameter of the primary nanosphere is less than 5nm; and a ratio of the primary nanospheres to the secondary nanospheres is 10: (1 to 2). The ratio is a mass ratio. Further, the primary nanospheres are located in a built space of the secondary nanospheres. The invention also discloses a preparation method of the yttrium oxide dual-level nanospheres. Compared with an ordinary direct liquid phase precipitation method, a subject matter is high in spheroidization degree and crystallization degree and smooth in surface, thereby not only avoiding the clustering phenomenon, but also significantly reducing the low-impurity mechanical impurities, so that the physical performance of the product is excellent, and the chemical purity is high.