Abstract: Trading behavior in a game of buyers and sellers is not only a stochastic proces s, but also reflects the equilibrium of the existence and consistency. Based on a newsvendor model, the structure of information asymmetry commodity trading mar ket is designed and constructed. According to updating values of information, de finitions of two-stage rational expectation equilibrium are presented and prope rties on the equilibrium condition are analyzed. These findings reveal that payo ff of inventory level in rational expectations equilibrium is larger than in non equilibrium. Finally, a numerical example with normal demand function is analyze d to compute information value with updating information and verify the validity of the rational expectations equilibrium.