This research was to investigate beneficial impact and molecular mechanism of B. coagulans on piglets intestine. Twenty-four 21 days old weaned piglets were allotted to three treatments: control group (basal diet), B6 group (basal diet + 2×10⁶ CFU/g B. coagulans), B7 group (basal diet + 2×10⁷ CFU/g B. coagulans). The results showed that compared with control group, B6 and B7 group significantly decreased diarrhea rate and the concent of CHOL, GGT and DAO in plasma; decreased villus height and increase crypt depth in jejunum and ileum; increased the activities of SOD and CAT and decreased the concent of MDA and H₂O₂ in intestine. These data suggested that supplementing B. coagulans had beneficial impacts on promoting nutrients metabolism, maintaining intestinal integrity and alleviating oxidative stress and diarrhea. Futher research of molecular mechanisms showed that, these beneficial impacts were regulated by changing expression levels of related proteins (including HSP70, Caspase-3, Bax, Villin and Occludin), and genes (including RPL4, IFN-α, IFN-β, IFN-γ, MX1, MX2, OAS1, IL-1β, IL-4, CXCL-9, CCL-2, AQP3, SGLT-1, LPL, INSR and b^0,+AT), and altering community composition of gut microbiota (particularly family Clostridiaceae, Enterobacteriaceae, and Veillonellaceae and genus Prevotella, Turicibacter, and Lactobacillus).