Abstarct: The objective of this thesis is to present a market baxsed expiation planning approach for Iranian power transmission network at 2016. The presented approach considers both random and non-random uncertainties. This approach considers liquidity and promotion of competition as the main desire of customers and tries to increase competition level by transmission expansion planning. To this end, first the data of Iranian power transmission network was processed and perunit single line diagram of the network was prepared. Then random and non-random uncertainties in planning horizon were identified. Peak load was forecasted for each seasons of 2016. Average electrical energy price were also predicted. Generation expansion plans were identified. Then baxse on the generation expansion plans, forecasted peak loads, and predicted energy price, eight different scenarios were identified for 2016. Locational marginal prices were computed for each bus in each scenario. baxse on the classification of locational marginal prices a set of transmission lines were proposed as expansion candidates. Then, seventeen practical expansion plans were suggested by classifying expansion candidates. The merit of expansion plans were evaluated by computing a market baxsed criterion. The final plan was selected using risk assessment of expansion plans in different future scenarios. Comparison of the under construction expansion plans with the proposed expansion plans shows that twelve out of forty eight of proposed transmission lines are under construction by Iranian grid manage company. This comparison confirms the precision and accuracy of the proposed metho