Ultrasonic-assisted synthesis and separationof of fatty acid ethyl esters by transesterification of soybean oil with ethanol were investigated. An increased reaction rate was observed by use of ultrasound irradiation during the transesterification of soybean oil. The resulting product mixtures were purified with deep eutectic solvent synthesized by choline chloride and urea.Washing temperature, DES amount and duration of washing process at three levels were assigned as the control variables. The effect of the temperature and duration of the washing on glycerin and KOH removing efficiency was also investigated. AT the volume ratio of DES solvent to product 1:1, temperature is 70 ï°C, and washing time 6 min, the residue of glycerin in the upper layer of products is as low as 0.01007% after treatment, and no alkaline was detected in the fatty acid ethyl esters product.