In electricity market,if the state of unit economy operation is known,it can provide infinite help for generating corporation in balancing the risk of quoted price and profit.If the price bidding is only based on the generation cost,the unit will be compelled to shutdown frequently and the benefit space will be lost because of lacking of flexibility in price competing.In this paper,based on the principle of maximum profit,a mathematical model of unit which is unit economy operation is presented.An improved Particle Swarm Optimization algorithm is used in the model,which is proved to be excellent.It provides generating corporations with a more flexible and effective method when compared with analyzing and predicting results of traditional project.