Monocyts, macrophages and endothelial cells can be activated by lipopolysaccharide(LPS), induced cytokines synthesis and secretion, resulting in systemic inflammatory reaction. The transmembrane signal transduction of LPS plays key role in activation of cells. This article summarizes mainly the Toll like receptor TLR2 and TLR4 that is relative with LPS, summing up their construction features, ligands, regulation of gene expression and signal transduction mecharism. It is Toll like receptor that transducts the LPS signal into cells, and activates NF κB signal pathway, inducing expression of the effective gene.