Aim To investigate the effects of quercetin (QUE), isorhamnetin (ISOR) and norepinephrine (NE) on collagen synthesis of cultured human aortic vascular smooth muscle cell (VSMC). Methods Human aorta VSMC was cultured with QUE, ISOR, NE, phentolamine(Ph). Collagen synthesis was evaluated by measuring 3 H-proline incorporation. Results NE 10 μmol/L could stimulate collagen synthesis of VSMC, and the most effects of the stimulation occurred at 72 h. The effects can be inhibited by Ph. QUE and ISOR could inhibited collagen synthesis of VSMC. When VSMC were treated by 1～200 μmol/L of QUE or ISOR, the best inhibitory effects occurred at 200 μmol/L. There were dose-dependent inhibitory effects in different concentration of QUE and ISOR and the best effect of QUE occurred at 72 h. QUE and ISOR markedly inhibit collagen synthesis of VSMC induced by NE in a dose-dependent manner and the best effects occurred in 72 h after treated with QUE or ISOR. At the same time QUE and ISOR had cooperative effects on inhibition of the stimulation of NE. QUE and ISOR had more powerful inhibitory effect on collagen synthesis of VSMC co-incubation with NE than without NE. QUE and ISOR also had more powerful inhibitory effect on collagen synthesis of VSMC co-incubation with NE than Ph. Conclusions QUE and ISOR could effectively inhibit the collagen synthesis of VSMC, especially inhibit the collagen synthesis of VSMC stimulated by NE.