Objective: To explore the effect of Na+/K+ in the intestinal environment on the interaction between soy hull polysaccharide (SHP) and intestinal mucus， and its effect on the diversity of intestinal flora. Methods: Molecular docking and molecular dynamics simulation were used to analyze the main binding force and complex stability of the target protein and soybean seed coat polysaccharide after Na+/K+ treatment. The effects of SHP and mucin on the changes of OTU and species abundance of intestinal flora after Na+ treatment was detected by 16S rDNA genomics. Results: The main force of SHP binding to mucin after Na+/K+ treatment was hydrogen bond. Within 100 ns， the RMSD value， RSMF value， Rg value and the number of hydrogen bonds of the complex structure fluctuated slightly. The secondary structure β-sheet of mucin mainly existed in anti-parallel mode after Na+ treatment， while the secondary structure β-sheet of mucinmainly existed in parallel mode after K+ treatment. The binding free energy [(196.7±26.7) kJ/mol] and the contribution of amino acid residues (18.18 kJ/mol) of SHP to mucin after Na+ treatment were greater than those after K+ treatment [(158.5±26.7) kJ/mol and 10.63 kJ/mol， respectively]. In the presence of Na+， the diversity of intestinal flora was up to 284 OTUs when SHP was used as a substrate for 8 h， and the abundance of various dietary fiber degrading bacteria was increased， and the abundance of Escherichia coli-Shigella was decreased. At the same time， the abundance of Bifidobacterium and Lactobacillus was also decreased. Conclusion: After Na+ treatment， the binding ability and stability of SHP and mucin are higher， and the diversity and abundance of intestinal flora are affected. Na+ treatment has a potential effect on the whole intestinal function of dietary fiber.

molecular simulation  /  ions  /  polysaccharide  /  mucin  /  intestinal flora