Abstract: A moissanite ornament, wherein the surface of the moissanite is coated with a diamond film. A method for coating a diamond film on a surface of a moissanite, including: Step 1: performing ultrasonic grinding pretreatment on the moissanite ornament in the nano-diamond powder suspension; Step 2: taking the moissanite ornament out from the nano-diamond powder suspension, and washing clean; Step 3: pressing the moissanite ornament into a preset shape-preserving sample platform to maintain; Step 4: placing, the moissanite ornament together with the shape-preserving sample platform into a diamond film deposition furnace to perform a plasma treatment; Step 5: introducing methane to conduct in-situ diamond film deposition. The moissanite coated with the diamond film on the surface provided by the present disclosure can greatly improve the surface hardness while maintaining the optical properties of the moissanite, thereby improving the scratch resistance performance of the moissanite.