Abstract: There are abundant pectin polysaccharides in our daily diet.Investigating the digestion of pectin in human body is helpful for the development of pectin polysaccharide products which are more easily absorbed by our body.In this study,the effect of pectin concentration and enzymatic hydrolysis time on the pectin structural characteristics was examined by using single factor experimental design method.The content of pectin in the external simulation of gastric and gastrointestinal tract in vitro was investigated by carbazole colorimetry,while the structure of pectin was analysis by Atomic Force Microscope (AFM) and Fourier Transform Infrared Spectroscopy (FTIR) methods.The results showed that with the increasing of digestion time,the galacturonic acid content (from 40.10% to 18.54%) and reducing sugar content (from 41.62% to 13.64%) decreased after digested by gastric juice.There was no significant difference (P>0.05) in the galacturonic acid and reducing sugar content after digested by intestinal fluid.The FTIR results showed that pectin polysaccharide degraded,and the esterification degree gradually decreased throughout the digestion progress.However,the esterification degree of pectin had no obvious difference after digested by intestinal fluid.The result of AFM indicated that with the increase of digestion time of gastric juice,the number of aggregates and the molecular chain width of pectin decreased and the pectin polysaccharide degraded,while the nanostructure of pectin had no significant change after intestinal digestion.It was concluded that the degradation of pectin was mainly affected by gastric juice..