A preparation method of liquid hindered phenol carboxylic ester antioxidant includes steps of: reacting hindered phenol carboxylic-acid methyl ester in formula (I) with branched fatty alcohol of C10-C36 under the presence of solid alkaline catalyst, wherein the solid alkaline catalyst is NaY zeolite carrying magnesium oxide, the catalyst contains 1-50% of the magnesium oxide by mass, the formula (I) is shown in the description, and in the equation (I), R1 and R2 are C1-C8 alkyl, and R3 is C1-C5 alkylene. By using the inventive method, productivity is improved, reaction temperature is reduced, reaction time is shortened, and the color of products is modified.