Abstract: Objective To observe the effect of G protein-coupled receptor APJ endogenous ligand apelin-13 on the proliferation of vascular smooth muscle cells (VSMCs),and investigate whether the effect is related to apelin/APJ-pERK1/2 -cyclin D1 signal transduction pathway. Methods The cell proliferation were measured by MTT assay and the expression of cyclin D1 and pERK1/2 were determined by Western blot.The rusults showed that apelin-13 can stimulated VSMC proliferation in a concentration-dependent manner. Western blot analysis showed that apelin-13 stimulated the expression of cyclin D1 and pERK1/2. The ERK1/2 inhibitor PD98059 decreased the expression of pERK1/2 induced by apelin-13. Similarly, PD98059 partially diminished the expression of cyclin D1, and inhibited the VSMCs proliferation stimulated by apelin-13. Conclusion Apelin-13 can stimulated the proliferation of VSMC and the effect was possibly mediated by apelin/APJ- pERK1/2-cyclin D1 signal cascades.