Aim To investigate the effect of water extract propolis on cholesteryl ester accumulation in human umbilical artery smooth muscle cell (HUASMC),and explore the mechanism of water extract propolis on inhibition of atherosclerosis and it's implications. Methods HUASMC was cultured by explant method,foam cell model derived from smooth muscle cell was prepared:coculturing HUASMC with ox-LDL in concentration of 25,50 and 75 mg/L respectively,the intracellular total cholesterol (TC)and free cholesterol(FC) at 12,24,36,48 and 60 h were measured by high performance liquid chromatogram,coculturing HUASMC with ox-LDL in concentration of 50 mg/L for 48 h as the optimum condition for foam cell formation. Cultured HUASMC were randomly divided into 5 groups:control group (without any drug),model group (50 mg/L ox-LDL for 48 h),propolis groups (50 mg/L ox-LDL and 50 mg/L,100 mg/L,200 mg/L WEP respectively for 48 h). Intracellular total cholesterol and free cholesterol were measured by high performance liquid chromatogram,the content of cholesterol ester (CE) was obtained by subtracting the FC from TC. Results HUASMC were cocultured with 50 mg/L ox-LDL for 48 h,the ratio of intracellular CE/TC was more than 50%,and the cells were transformed into foam cell. The content of intracellular CE in model group was more than that in the control group (P<0.01); The content of intracellular CE in 50 mg/L,100 mg/L and 200 mg/L WEP groups were less than that in the model group (P<0.01),and with the increase of the concentration of WEP the content of intracellular CE had the tendency of decreasing. Conclusion ox-LDL can induce the cholesteryl ester accumulation in cultured HUASMC in vitro,and transform it into foam cell,simultaneously it can raise the apoptosis index of HUASMC. WEP can reduce the extent of intracellular CE accumulation in HUASMC induced by ox-LDL,and that maybe one of the mechanisms of it's anti-atherosclerosis effect.