The invention relates to the technical field of a new material, especially to a lens. A preparation method comprises: providing a transparent substrate; adopting a microwave plasma chemical vapor deposition method, leading a mixed gas of methane, hydrogen and oxygen into a reaction chamber, controlling the temperature at 400 DEG C, the microwave power at 1.5-2.5 kw, and the air pressure at 20-30 mbar, and allowing a hydrophilic diamond-like film to form at the lower surface of the transparent substrate; and adopting a microwave plasma chemical vapor deposition method, leading a mixed gas of methane, hydrogen and oxygen into the reaction chamber, controlling the temperature at 400 DEG C, the microwave power at 3-4 kw, and the air pressure at 35-45 mbar, and allowing a hydrophobic diamond-like film to form at the upper surface of the transparent substrate. Through controlling reaction conditions, a hydrophilic/hydrophobic diamond-like film is obtained. The diamond-like film is well applied to prepare a lens.