Objective:To explore effects of H2S on expression of COX-2 on macrophages(RAW264.7) and formation of macrophage-derived foam cells. Methods:RAW264.7 foam cell model induced by low-density lipoprotein (Ox-LDL) is established,then added with different concentrations of H2S. Detection of foam cell formation is conventionally practiced by Oil Red O staining. The expressions of COX-2 mRNA and protein are detected by real-time qPCR and Western blot respectively. Results:A significant increase of the production of COX-2 and the deposition of intracellular lipid was observed. Different concentrations of H2S can considerably reduce the expression of COX-2 and the deposition of intracellular lipid induced by the Ox-LDL,especially the concentration of 250 μmol/L and the difference is statistically significant(P < 0.05). Conclution:H2S can significantly reduce the expression of COX-2 in macrophages(RAW264.7 )and inhibit the formation of foam cells .