The service reliability research of electric power communication network is mainly based on the number of business links, without taking the differences of traffic flow into account. By analyzing the structure, types and distribution of communication service, a transmission model of communication network service is established and a method of reliability analysis of distribution communication network based on traffic flow is proposed. Through an instance, the advantage of this method compared with the method which is based on the number of business links is analyzed. Simulation results verify the feasibility of this method.