Tung oil acid diethanolamides was prepared by the transmidation reaction between tung oil and diethanolamine, and a new purification process was put forward. The structure of tung oil acid diethanolamides has been analyzed with Fourier Transform Infrared Spectrometer (FTIR) and Ultraviolet Visible Spectrometer (UV spectrometer). The result shows the characteristic FTIR bands of the product correspond to the relevant bands of tung oil acid diethanolamides, like hydroxyl, acylamino and conjugated double bond; The UV absorption bands of tung oil and tung oil acid diethanolamides are quite similar, both have strong absorption in the range 200~270 nm and 283~315 nm, but the UV absorption bands of tung oil acid diethanolamides present red shift under the influence of acylamino and hydroxy.