Objective To observe the effects of lipopolysaccharide (LPS) on B cell function and the related signal transduction pathways. Methods Freshly purified splenic B cells (CD19⁺ B) of mice were isolated by magnetic activated cell sorting. After stimulation with LPS, the culture supernatants were collected for immunoglobulin isotyping by cytometric bead array (CBA) technology. Flow cytometry was used to analyze costimulatory molecule expression and culture supernatants were also collected for measuring IL-6, IL-10, IL-12p70 and TNF by CBA technology. PD98059 (ERK inhibitor), SP600125 (JNK inhibitor), SB203580 (p38 MAPK inhibitor) and PDTC (NF-κB inhibitor) were used to study the signal pathways for the induced secretion of IL-6, IL-10 and TNF in B cells. Results LPS induced IgG₁ -κ and IgM-κ production, up-regulated the expression of CD40, CD80, CD86 and MHC class Ⅱ, and promoted IL-6, IL-10 and TNF secretion by B cells. Furthermore, JNK, p38 MAPK, and NF-κB pathways regulated the secretion of IL-6, IL-10 and TNF in B cells. Conclusion LPS can regulate B cell function by inducing Ig production, cytokine secretion, and expression of costimulatory molecules.