Proliferation and migration of vascular smooth muscle cells (VSMCs) are important events in the development of diabetic atherosclerosis. Previous studies have suggested that K(Ca)3.1 channels participate in atherosclerosis and coronary artery restenosis. In the present study, we attempted to clarify the roles of K(Ca)3.1 channels in the proliferation and migration of VSMCs using experimental type-2 diabetes rat serum and aortic smooth muscle cells (SMC) prepared from non-diabetic rats. mRNA and protein levels and current density of K(Ca)3.1 channels were greatly enhanced in cultured VSMCs treated with diabetic serum. In addition, diabetic serum promoted cell proliferation and migration in cultured VSMCs, and the effects were fully reversed in the cells treated with the K(Ca)3.1 channels blocker TRAM-34. In conclusion, serum from diabetic rats increases the expression of K(Ca)3.1 channels and promotes proliferation and migration of VSMCs to possibly participate in vascular remodeling in diabetes.