In the electricity market environment,it has become a major concern for generation company of how to build optimal bidding strategies.The problem of developing optimal bidding strategies for generation companies in the electricity market environment with transmission network congestion take into account is systematically investigated,and a two layer optimal model is built under the bidding behaviors of rival generation companies is known,and this model is solved by genetic algorithm. The simulation results of applying the proposed method to IEEE 14-bus test system show that the proposed method can be adopted to guide the drafting of bidding strategy.