Abstarct: Network expansion planning is inevitable due to the electric load growth. As important planning stage, regional electricity companies determine the appropriate location of transmission and distribution substations considering load growth and demand request of large industrial consumers. Current method of determining the substation location indicates that the expert knowledge is used. However, due to the lack of a system for taking all effective criteria and their value, the substation location is normally chosen by an expert person or a group. Due to the impact of the substation location on the transformers loading, losses, and high costs of construction and operation of substations, it is necessary to use a decision support system for determining appropriate location of substation. The proposed method determines the main criteria influencing the choice of location substation, and evaluates the importance of each criterion by analytic hierarchy process. baxsed on the weighted average of scores of all main criteria and sub-criteria, the substation locations are listed in merit, and accordingly, the best one is chosen. Implementation of the proposed method on a real case study in Yazd province, Iran, shows its applicability in choosing appropriate location of substation.