Aim To explore the role of intracellular free calcium in the proliferation of cultured vascular smooth cells (VSMC) stimulated by neuropeptide Y (NPY). [WT5”HZ]Methods The cultured VSMC of rat were used for experiments at passage 3 to 5. We applied the method of cellular culture, MTT colorimetric assay and quantitative immunocytochemistry through laser scanning confocal microscope (ACAS570) to detect the effect of NPY on the proliferation of VSMC. At the same time, the effect of NPY on the intracellular free calcium concentrations were also quantitatively detected in VSMC. Results It was observed that exposure of cultured VSMC to NPY could stimulate the proliferation of VSMC, the MTT OD values and expression of proliferating cell nuclear antigen (PCNA) increased in cultured VSMC respectively compared with control group (P<0.01).At the same time, the intracellular free calcium concentrations in VSMC were also increased by NPY. Conclusion The proliferation of cultured VSMC stimulated by NPY is mediated by intracellular free calcium in cultured vascular smooth muscle cells.