Tung oil and glycerol were used to synthesize tung oil-based polyol with sodium methoxide as catalyst through interesterification, and a new purification process was put forward. The structure of dihydroxy tung oil acid ester has been characterized by Fourier transform infrared spectrometer (FTIR) and Ultraviolet Visible Spectrometer (UV spectrometer). The result of FTIR shows: The product corresponds to the dihydroxy tung oil acid ester, which contains characteristic absorption peaks, such as: hydroxyl, ester and conjugated double bond; The result of UV spectrometer shows: The UV absorption bands of tung oil and dihydroxy tung oil acid ester are very similar, but the latter has an absorption in 245 nm because of the absence of hydroxyl, which demonstrates the product is the expected one.