The invention belongs to the technical field of semiconducting material synthesis and discloses petal-shaped cuprous oxide and a preparation method and application thereof. According to the method, the cuprous oxide is driven by a photocatalysis fuel cell to be reduced and deposited. Nano TiO2 serves as a phstocatalyzer, amylaceum serves as fuel, cupric acetate serves as a copper source, TiO2-decorated conductive glass serves as the anode, conductive glass serves as the cathode, and thus the ultraviolet excitation photocatalysis fuel cell is formed; and meanwhile, deposition of the petal-shaped cuprous oxide on the conductive glass and dual conversion from light and chemical energy to electric energy are achieved. According to the deposition method, operation is easy, the cost is low, the energy utilization rate is large, and non-toxicity and environmental-friendliness are achieved.