OBJECTIVE To investigate the relationship between small intestinal bacterial overgrowth (SIBO) and Endotoxin (ET) concentration in peripheral blood, and levels of toll-like receptors (TLR) 2 and TLR4 expression on surface of peripheral blood mononuclear cells (PBMCs) in patients with ulcerative colitis. METHODS An experimental study. METHODS The First Hospital of Hebei Medical University, from July 2018 to October 2019. METHODS The 130 patients with ulcerative colitis were included in case group. Another 72 healthy cases were selected as control group. SIBO, ET, TLR2, and TLR4, were determined, and compared. RESULTS Positive rate of SIBO in case group was higher than that in control group (p <0.001). Lactulose hydrogen breath test (LHBT) intestine set value, peripheral blood ET concentration, and TLR2 and TLR4 expression levels on surface of PBMCs in case group were higher than those in control group (all p <0.001); the above indexes in SIBO-positive patients in case group were higher than those in SIBO-negative patients in case group (all p <0.001). Pearson's correlation analysis showed that LHBT intestine set value of SIBO-positive patients in case group was positively correlated with ET concentration, and TLR2 and TLR4 expression levels on surface of PBMCs (r= 0.910, p <0.001; r = 0.970, p <0.001; and r = 0.965, p <0.001 respectively). ET concentration of SIBO-positive patients in case group was positively correlated with expression levels of TLR2 and TLR4 on surface of PBMCs (r=0.962, p <0.001; and r = 0.829 p <0.001 respectively). CONCLUSIONS Patients with ulcerative colitis are easy to occur SIBO, and SIBO increases blood endotoxin, TLR2 and TLR4 levels. Synergistic effects of endotoxin and endotoxin receptors TLR2 and TLR4 overexpression mediate body inflammation and may be involved in progression of ulcerative colitis. Patients with ulcerative colitis with excessive growth of small intestinal bacteria are more likely to have hypertoxemia.