Abstract: 2-iso-Propyl-1,3-dioxy-5-cycloheptene was prepared by the aldol reaction between cis-butene glycol and iso-butyl aldehyde,with p-toluene sulfonic acid as catalyst,under the reaction temperature of 110-120 ℃ for 5 h.The optimum mole ratio of the reactants was found to be 1 to 1.2 for cis-butene glycol to iso-butyl aldehyde.Gas chromatography with the strongly polar capillary column (60 m×0.25 mm) was used for the determination of 2-iso-propyl-1,3-dioxy-5-cycloheptene in the reaction mixture,giving results of the product over 98% in mass concentration.Moisture of the product synthesized was found to be less than 0.1% as determined by the karl fisher titrimetry.