The invention discloses a preparation method for styrenated phenol. The preparation method comprises the following steps: adding phenol and p-toluenesulfonic acid into a container, introducing nitrogen, carrying out sufficient stirring with a stirring device at a rotating speed of 300 to 350 r/min, carrying out heating to 85 DEG C and then starting addition of styrene drop by drop, wherein the addition lasts for less than 2.5 h; after completion of the addition of styrene, carrying out heating to 120 to 130 DEG C at a constant rate and maintaining the temperature for 2 to 2.5 h; and stopping heating, adding triethylamine into a mixture obtained in the previous step, carrying out full stirring, then successively carrying out filtering, pumping filtration and vacuum distillation until no liquid is distilled off, carrying out cooling to 80 DEG C or below, and then carrying out discharging. According to the invention, the catalyst p-toluenesulfonic acid used in the invention is an organic acid and exerts good promotion effect on the alkylation reaction of phenol with styrene; the acidity of p-toluenesulfonic acid is weaker compared with inorganic strong acids like sulfuric acid and hydrochloric acid, so corrosion to reaction equipment is small; and reaction process is smooth and steady, reaction temperature is easy to control, and prepared styrenated phenol has a shallow color.