Reasonable planning and construction of 5G access network will help provide new generation network functions such as large bandwidth, low latency and multiple access. In order to improve the reliability of 5G access network, a high reliability wavelength division multiplexing passive optical networks(WDM-PON) architecture is designed for 5G access network by combining tree topology with dual fiber ring topology. Among them, the tree topology can ensure the transmission quality of the network in normal operation, the dual fiber ring topology can realize the flexible switching between nodes in case of failure, and provide fault protection. The signal transmission under normal operation and fault protection mode is analyzed. Through theoretical calculation and experiments on signal quality and delay, it is proved that the proposed network structure is more reliable than the conventional tree topology.