The invention discloses a preparation method of a layered flower-like cuprous oxide nanomaterial. The method comprises the following steps: with copper salt, ascorbic acid and polyvinylpyrrolidone as raw materials and distilled water/glycerin as a solvent, reacting for 5-40min under ultrasound; and centrifuging the obtained brick red precipitate, and washing and drying to obtain the layered flower-like cuprous oxide nanomaterial. In the method, the raw materials such as copper salt, ascorbic acid, glycerin and polyvinylpyrrolidone are cheap and easily available, the cost is reduced, and the operation steps are simplified. Meanwhile, the prepared layered flower-like cuprous oxide nanomaterial has very large specific surface area and potential application value in terms such as photocatalytic degradation dye, gas sensitivity, energy storage and lithium batteries.