Qingke　β-glucan　(QBG),　a　gastrointestinal　indigestible　grain　polysaccharide,　is　used　as　prebiotic　and　delivery　carrier　to　mediate　gut　microbiota,　while　the　mechanism　of　QBG　of　different　MWs　degraded　by　the　gut　microbiota　remain　uncertain.　In　this　study,　we　investigated　the　impacts　of　QBG　with　different　MWs　on　gut　microbiota,　SCFAs,　and　the　degrading　degree　of　polysaccharides　in　vitro　fermentation.　QBG　groups　significantly　increased　the　total　SCFAs,　which　is　consistent　with　the　results　predicted　by　PICRUSt2　based　on　the　KEGG　pathway.　The　27　functional　genes　associated　with　SCFAs　metabolism　were　identified.　Acetate　and　propionate　synthesis　was　primarily　mediated　by　the　pta,　ackA,　and　ACSS　genes,　whereas　butyrate　production　mediated　by　the　ptb,　buk,　and　atoA　genes.　The　low-MW　QBG　produced　more　SCFAs　than　the　high-MW　QBG　after　fermentation,　suggesting　that　polysaccharide　MW　influences　its　biological　functionality.　These　findings　support　polysaccharide-based　gut　microbiota-targeting　drug　and　food　development.　©　2025