Aim To observe the role of quercetin(QUE),isorhamnetin(ISOR) and norepinephrine(NE) on the proliferation of human aortic vascular smooth muscle cell(VSMC). Methods The effects of QUE,ISOR and NE on these VSMC growth and DNA synthesis was investigated by cell counting,~3 H-thymidine incorporation. Results QUE could inhibit proliferation and DNA synthesis of VSMC but these effects of ISOR was weaker than that of QUE.When VSMC were treated by 1～200 μmol/L of QUE or ISOR,the best inhibitory effects occured at 200 μmol/L.There were dose-dependent inhibitory effects in different concentration of QUE and ISOR.NE 10 μmol/L could stimulate proliferation and DNA synthesis of VSMC.The effects could be inhibited by phentolamine(Ph).QUE and ISOR markedly inhibited proliferation and DNA synthesis of VSMC induced by NE in a dose dependent manner.At the same time QUE and ISOR had cooperative effects on inhibition of the stimulation of NE.QUE and ISOR also had more powerful inhibitory effect on proliferation and DNA synthesis of VSMC co-incubation with NE than Ph.There were no cyto-toxic effects on VSMC treated with QUE and ISOR. Conclusion These results indicated that QUE and ISOR had no cyto-toxic effect on VSMC cultured in vitro and could effectively inhibit the proliferation and DNA synthesis of VSMC,especially inhibit the proliferation and DNA synthesis of VSMC stimulated by NE.