Non-uniform expansion of cardiovascular stents, which exists widely in experiments, has a large influence on stent safety, but has seldom been studied in depth until now. In this paper we use a folded balloon with friction to expand a stent through finite element method (FEM), and study how this influences non-uniform expansion of the stent. The simulations were carried out using ABAQUES software. The results show that the stent expands non-uniformly only when the fold and friction are considered together in the FEM model. The extent of non-uniformity during expansion increases with rising friction coefficient values; with the same friction coefficient but different stent locations on the balloon the extent of non-uniform deformation is different. On the other hand, compared to a tri-folded balloon, a six-folded balloon clearly decreases the expansive non-uniformity, which means that by increasing the number of the folded parts of balloon the stent expands more uniformly.