Power system communication network plays a foundational role on the security and stability of power grid. Towards the communication transmission network of power system, the technical realization principle and time synchronization technology of SDH and PTN networks were analyzed. According to the performance requirements of the power grid for the transmission network carrying E1 and Ethernet services, a network test platform was built under the laboratory environment, and the performances of the transmission network in different services were tested. The experimental results show that SDH and PTN networks have favorable capacity for carrying E1 and Ethernet services, which can satisfy the performance requirements of the transmission network. Finally, some suggestions are presented to further improve the reliability of SDH and PTN transmission networks.