Aim To evaluate the effect of water extract propolis(WEP) on human umbilical artery smooth muscle cell proliferation(HUASMC) induced by angiotensinⅡ(AngⅡ) in vitro and explore the underlying mechanism. Methods HUASMC were cultured by the explant method and incubated with 50 mg/L,100 mg/L and 200 mg/L WEP. HUASMC number was assessed by cell counting;Flow cytometry was used to test cell cycle;Proliferating cell nuclear antigen (PCNA) of HUASMC was detected by immunocytochemistry staining;Superoxide dismutase(SOD) and maleic dialdehyde (MDA) in HUASMC culture medium superior was measured with spectrophotometer;Apoptosis was evaluated by terminal -deoxynucleotidyl transferase mediated nick end labeling(TUNEL).Results Compared to model group,the numbers,PCNA expression,MDA,Apoptosis Index of 100 mg/L and 200 mg/L WEP were lower(P<0.01),while the Percentage of the Cells in G_0/G_1 phase and SOD was higher(P<0.01).Conclusion Certain concentration of WEP can prevent HUASMC proliferation effect mediated by AngⅡ;the mechanism about WEP effect may be associated with arresting G_1 to S progression,decreasing PCNA expression and improving the antioxidation of HUSMC.