The invention relates to a carbon-fiber-reinforced polyformaldehyde gear which is prepared from polyformaldehyde resin, chopped carbon fiber, molybdenum disulfide, calcium stearate, coupling agent and phenolic resin. The invention also relates to a preparation method of the carbon-fiber-reinforced polyformaldehyde gear, which comprises the following steps: carrying out composite surface treatmenton the carbon fiber; and putting the raw materials into a high-speed mixer according to the percentage in the formula, sufficiently mixing, granulating, and carrying out injection molding in an injection molding machine. The composite surface treatment, which is carried out on the chopped carbon fiber, greatly improves the wettability of the carbon fiber surface, and maximally enhances the interfacial adhesiveness between the carbon fiber and the polyformaldehyde matrix, thereby greatly enhancing the mechanical properties of the composite material. The gear prepared from the carbon-fiber-reinforced wear-resistant polyformaldehyde has the advantages of low specific gravity, low noise, favorable wear resistance, favorable self-lubrication effect, chemical corrosion resistance, high specificstrength, large specific modulus, small thermal expansion coefficient, static resistance and the like, and does not produce sparks, thereby being capable of replacing the original steel part. In addition, the invention reduces the labor intensity of workers, and lowers the energy consumption.