The invention discloses cage-shaped nano zinc oxide and a preparation method thereof, and relates to a method for preparing zinc oxide. The cage-shaped nano zinc oxide material has a multilayer cage-shaped structure consisting of nano zinc oxide granules. The preparation method for the cage-shaped nano zinc oxide comprises the following process steps: (1) dissolving zinc acetate and glucose in 80 milliliters of deionized water, ultrasonically treating the solution for 10 minutes to form cleared solution, then transferring the cleared solution to a polytetrafluoroethylene inner container, putting the inner container into a stainless steel autoclave, and hermetically reacting the solution; (2) putting the autoclave into an oven to perform thermal reaction for 12 hours, naturally cooling a reaction product to room temperature after the reaction to obtain black powder, then centrifugally washing the black powder for multiple times by using deionized water respectively, washing the black powder by using ethanol to remove a little amount of carbon-containing substance in the product, and drying the washed black powder at the temperature of 60 DEG C; and (3) putting the powder into a muffle furnace and calcining the powder to form the cage-shaped nano zinc oxide material. The cage-shaped nano zinc oxide material is used in the fields of photocatalyst, optical devices, sensors, solar cells, medicinal capsules and the like.