A new bi-level programming model of multistage transmission network expansion planning (TNEP) based on double-bidding based pool electricity market is presented in the paper. Open access transmission brings new challenges to transmission planning. From the transmission company's view, the goal of optimal transmission planning scheme should not only bring the optimal transmission profit in the market, but also ensure high operation security and reliability. In this paper, the upper level program considers transmission profit maximization in long-term planning, the lower level program considers the social welfare maximization in short-term operation. Furthermore N-1 security constraints are also considered in the model. A hybrid algorithm integrated with niche genetic algorithm and prime-dual interior method is used to solve the bi-level programming model of the transmission network expansion planning. Test results of the 18-bus system and real world 77-bus system show feasibility and right of the method.