Abstract: With the deepening of the electric power system reform, electricity market has attracted attentions from both academic and industrial societies. In this paper, a bilateral game model with incomplete information between the electricity generation and selling enterprises is established, which considers the direct electricity purchase prices and amount as the strategy sets of the both sides. In order to forecast the direct electricity purchase prices, the factor of generation costs is introduced, which uses the co-integration theory to construct the relation between the direct electricity purchase prices and the generation costs. Further more, to forecast the direct electricity purchase amount, the similar days method is adopted to ensure the information sharing demand between both sides. Finally, the equilibrium solution of the bilateral game is obtained by using Nash equilibrium, and the model has been proved by simulation.