With the continuous development of the smart grid,the energy internet,the application of cloud computing,big data,data mining and virtualization technology in the power industry,the electric power telecommunication has been una-ble to satisfy the requirements of the power system.As a new network architecture,software defined network (SDN) realizes decoupling of the control function and data transmission function,which is one of the choices of future electric power telecommunication network architecture.Based on the principle of SDN network that is discussed in the paper,the key technology of electric power telecommunication network based on SDN is shown in detail.And the key technologies are as follows:performance,security,scalability,delay,link reliability,fault tolerance and compatibility.What's more,this paper discusses the application of prospect of SDN in Power System with great prospect.