Aim To investigate the effects of platelet factor 4 (PF4) on the expression of Toll like receptors 2 (TLR2) in human umbilical vein endothelial cells-ECV304. Methods The effects of PF4 on the expression of TLR2 in ECV304 were determined by reverse-transcription polymerase chain reaction,Western Blotting and immunohistochemistry analysis. Results In comparison with blank group,the levels of TLR2 mRNA and protein upregulated (n=5,P><0.05) in time dependent manner in PF4 (100 μg/L) group,but it could not be inhibited by heparin. Using immunohistochemical staining and image analysis methods,the TLR2 expression in ECV304 in PF4 group was increased compared with blank group(0.060 399±0.020 998 vs 0.001 385±0.000 953,P><0.05). Conclusion PF4 promotes the expression of TLR2 mRNA and protein in human umbilical vein endothelial cells. The result of study is useful for platelet to play effect on innate immunity in chronic inflammatory such as atherosclerosis.