In this study, cationic etherifying agent 2,4-bis(dimethylamino)-6-chloro-[1,3,5]-triazine (BDAT) was synthesized by ultrasonic-assisted with cyanuric chloride and dimethylamine as raw materials. It was found that heterogeneous solid–liquid reaction can be proceed by ultrasonic-assisted in aqueous solution. Effects of reaction conditions including ultrasonic time, temperature, pH, ratio of the reactants and ultrasonic irradiation power on the yield of BDAT were studied. The yield of the target product reached 96% under the optimum conditions. The structure of the product was confirmed by IR, 1HNMR and MS spectroscopy.