With the rapid growth of various kinds of services demands, the traditional power network architecture has faced many problems and challenges. The software defined network (SDN) architecture has the advantages of flexibility, programmability and centralized control, which can be applied to power grid communication networks and solve the problems. Based on the common link failure problems in the network, the traditional 1+1 protection mechanism has fast switching speed, but it has very low utilizations of links. Based on SDN and the traffic characteristics of power grid communication networks, this paper proposes a traffic differential protection mechanism, which utilizes different protection mechanisms for different traffic flows. The simulation results show that the proposed protection mechanism can effectively reduce the link resource overhead and ensures reliable recovery of control traffic and other types of traffic flow. It achieves a good balance between resource overhead and delay of network. Keywords—power communication network; SDN; link protection; traffic differential protection