Objective To investigate the effect of neuropeptide Y(NPY) on free calcium concentration in vascular smooth muscle cell(VSMC). Methods The cultured VSMC was loaded with 10 ?mol/L Fluo-3, and were perfused with normal extracelluar fluid, non-calcium extracellular fluid plus 10 -6 mol/L _NPY, 1 ?mol/L nifedipine, 1 ?mol/L nifedipine+10 -6 mol/L _NPY. The intensity of the cells' fluorescence activated by the laser in 525 ?mol/L was detected with confocal microscope and analyzed with the Leica imagine system. Results The concentration of \_i was not changed after cultured with normal extracellular fluid[57.3+3.1 vs 53.7+2.9, fluorescence OD(FOD)]. _NPY increased \_i to maximum of 86.4?2.7 and gradually declined to 58.1?3.0 FOD (P