An infrared spectroscopy method for rapid quantitative determination of the degree of esterification (DE) of pectic polysaccharides was developed.Taking pectic polysaccharides from angelica sinensis as samples,the calibration curve was established between DE and the ratio of A1 730/(A1 730+A1 630).The square of the linear correlation coefficient was 0.822,indicating a good linear relationship between the DE and the absorbent area at 1 730 and 1 630 cm^-1.Using this method,the DE of pectic polysaccharides from angelica sinensis was determined to be between 42.36% and 54.06% for crude and purified samples respectively.The relationship between infrared spectroscopy data and titrimetrically determined DE values was investigated,indicating an excellent reproducibility.This method is characterized by less sample,simple manipulation,higher sensibility,and speedy analysis compared to chemical method and other instrumentations.FTIR shows a good feasibility and can be a rapid,alternative method to titrimetric analysis for DE determination.