The rapid development of communication services in the power distribution network poses challenges for existing wireless communications, and the deployment of a fiber optic network is costly and difficult. The emerging 5G technology has been piloted in power distribution networks, though the cost-effectiveness of its large-scale deployment remains unclear. This paper proposes an economic evaluation method for 5G planning in power distribution networks, considering the coupling relationship between power distribution and communication networks and the identification of important network nodes. First, the objective function to solve the planned number of 5G base stations is established. This is solved using the adaptive particle swarm algorithm and K-means algorithm. Second, the coupling relationship between the distribution and communication networks is discussed and quantified. The node importance of the coupling network is analyzed to identify the important nodes, and micro base stations or optical fibers are added to improve the reliability of the distribution network at the communication level. Finally, an economic evaluation index of 5G planning of the distribution network is established. The paper compares the economic solutions of 5G and 4G communications in city and town scenarios using the IEEE 123-node network as an example, and concludes that the economics of 5G are better than those of 4G.