As an important part of the power Internet of things, the distribution field area network is the "last mile" infrastructure of the power Internet of things. It can solve the communication problem of the last mile of the power Internet of things. In order to meet the high real-time and high reliability requirements of distribution field area network control services and improve the coverage and reliability of the network, a highly reliable and fast routing optimization algorithm based on Dijkstra algorithm is proposed. The field high-speed power line carrier and radio frequency communication methods of the field area network have complementary advantages. The nodes select the most reliable communication link to transmit data through the hybrid routing table, and consider the reliability and real-time constraints at the same time. The simulation results show that the high-reliability routing optimization algorithm of the distribution field area network can effectively increase the coverage capacity, the number of successfully transmitted services and the average routing reliability.