In the practice of purchasing decision making, many quantitative and qualitative factors must be considered, as well as the vagueness and imprecision among them, which makes the decision process more complicated and unstructured. Like fuzzy sets theory, vague sets theory is one of the methods that are used to deal with uncertain information. Since vague sets can provides more information than fuzzy sets, it is superior in mathematical analysis of systems with uncertainty. In this paper, a new approach based on vague sets is proposed to deal with supplier selection problem.