Abstract: In this paper, the multi\|objective genetic algorithm is applied to expansion planning of transmission network, then N-1 security criteria is taken as one of multiple objectives in the form of the penalty function, which can meet the higher requirement of safety of power grid planning. The optimal elites\|saving strategy is introduced into the multi\|objective genetic algorithm in this paper to avoid the loss of outstanding individuals and accelerate the convergence speed. In addition, fault ordering method is adopted as N-1 security criteria to improve computation efficiency. In the end, a standard example is simulated and the results show that taking N-1 security index as one of multiple objectives can obtain optimal solution that meet the requirement of N-1 security of power grid. In addition, the multi\|objective genetic algorithm will obtain optimal solution through comparing with traditional algorithm.