Abstract: Compared with the traditional method to obtain lignin by alkali extraction from Momordica grosvenori Swingle fruit residues,ultrasonic extraction was used for the dewaxed samples with 0.5 mol /L KOH at 40℃ for 2.5 h.The optimum extraction technology was as follows:ultrasonic irradiation time 90 min,temperature 40℃,constant temperature time 2.5 h.Under this condition,the total dissolved lignin increased from 5.04% to 8.60%,and the extraction rate increased from 4.91% to 8.40%.The yield of lignin was 56.19%.IR and molecular weight measurements of the alkali-soluble lignins were carried out.