The invention discloses a chroming automatic spray paint and a preparation method thereof. The spray paint is composed of components A and B, wherein the component A comprises 8-11 parts of petroleum resin, 2-5 parts of floating aluminum-silver paste, 18-23 parts of dimethyl carbonate, 2-5 parts of acetone, 3-6 parts of isopropanol, 17-25 parts of dichloromethane and 4-8 parts of isoparaffin, and the component B is LPG (Liquefied Petroleum Gas) by weight, wherein the ratio of the dosage of LPG to the weight of the paint materials is 0.52-0.56. The chroming automatic spray paint is free of environmental pollution and harmless to the atmosphere; the chroming automatic spray paint is stable in performance, applicable to different angles and spaces, good in sprayability, and high in jet rate; the spray paint is self-dry at the normal temperature and can be dry quickly; the paint film is high in fullness, has excellent combination properties such as metallic texture and flexibility, and also has strong metal mirror decoration effect which is comparable with that of electroplating; the paint film is also capable of effectively resisting ultraviolet radiation and enhancing the ageing resistance of the decorated article, and has wonderful anti-rusting and protection functions.