In order to meet the wide-area protection communication requirements of power system, and provide reference and theoretical basis for the engineering design of power system wide-area protection network and the assessment calculation of communication systems, according to SDH optical network communication theory and self-healing network reliability evaluation method, transmission link section failure probability and availability and other indicators are quantitatively analyzed using state space method. A reliability research method of layered regional protective communication backbone and regional networks is described, including the reliability model and availability assessment of SDH self-healing network and star networks, network redundancy and process layer device network structure. Illustration analysis shows that the path protection feature using SDH self-healing ring network can reduce the impact of fiber failure on the entire ring network reliability, and improving the reliability of the interface is the key of reliability of the SDH ring network.