The invention discloses a preparation method of double-sided zinc oxide nanocomb. The preparation method includes the steps of firstly, using nitrogen to blow and dry a substrate cleaned by ultrasonic, sputtering a layer of metal Al film on the substrate to serve as the Al source of hydrothermal reaction; secondly, sputtering a layer of zinc oxide seed layer with the thickness being about 25-50 nanometers to the substrate precipitated with the Al film; thirdly vertically placing the substrate precipitated with the Al film and the seed layer into a reaction kettle loaded with the mixed solution of zinc nitrate and ammonia water to perform the hydrothermal reaction; fourthly, naturally cooling to room temperature after the reaction, taking out the substrate, washing with deionized water, and drying under room temperature, wherein the product on the surface of the substrate is the double-sided zinc oxide nanocomb. The preparation method has the advantages that the double-sided zinc oxide nanocomb, a zinc oxide nano piece and a zinc oxide nanorod structure are prepared by regulating the thickness of the zinc oxide seed layer and using the one-step hydrothermal reaction, and the method is simple to operate, high in controllability, low in cost, suitable for large-area growth, applicable to various substrates, high in practical value, promising in application prospect, and the like.