The process includes the steps of ;(a) producing phenylallyleter(III) from the reaction of phenol derivatives(I) and crotyl derivatives(II) in base-solvent system such as sodium carbonate or calcium carbonate and acetone or low-grade alcohol; sodium hydroxide or calcium hydroxide and ethyleter, low-grade alkan or petroleum eter; sodium ethoxy or sodium methoxy and ethanol or methanol; (b) producing phenol derivatives(IV); (c) producing hemiacetal(V) from the oxidation of phenol derivatives(IV); (d) producing ortho-isopropylized phenol derivatives from the reduction of hemiacetal(V).