The invention discloses a low-viscosity turpentine-based monoterpene vinyl ester resin monomer and a preparation method and application thereof. The preparation method comprises the following steps of: under an oxygen-free environment, enabling turpentine monoterpene monomers to react with unsaturated carboxylic acid or anhydride to obtain monoterpene carboxylic acid or anhydride, then enabling the obtained monoterpene carboxylic acid or anhydride to react with unsaturated carboxylic acid glycidyl ester to obtain monoterpene unsaturated diglyceride, adding modifier for modification, and decolorizing by using activated carbon to obtain the turpentine-based monoterpene vinyl ester resin monomer, wherein the viscosity of the turpentine-based monoterpene vinyl ester resin monomer is 90-130mPa.s, the iodine value is 120-180 and the chromaticity through an iron-cobalt colorimetric method is 4-8. The turpentine-based monoterpene vinyl ester resin monomer prepared by adopting the preparation method has the advantages of low viscosity, low volatility, no toxicity, environmental friendliness and the like, and can be used as thinner of conventional unsaturated polyester resin; and cured resin has the advantages of good toughness, corrosion resistance, weather resistance and high product stability.