Traditional economic dispatching and market dispatching are two typical dispatching models in power system.However,there are some merits and demerits in the full eco-nomic dispatching and full market dispatching. In this paper,a hybrid dispatching model considering the free electricity tran-saction based on these two kinds of dispatching models is studied,and the mathematic model of the hybrid dispatching is developed. In the proposed model,the power is divided into two parts: the power participating in the market competition and the power not participating in the market competition. The former is fully competitive,which employs the market dispat-ching model while the latter is responsible for the adjustment of the power flow and the allocation of the network losses,which employs the economic dispatching model. Finally,the influence of different transaction ratios on the power system operation using the hybrid dispatching model is analyzed on the IEEE-30 bus system,and the optimal transaction ratio is determined.