In the planning process of the distribution network, due to the lack of statistical data, only theoretical reliability calculations and evaluations can be performed. However, the existing reliability assessment indicators are relatively rough and untargeted, and cannot well reflect the reliability management issues in different business areas (planning, maintenance, and operation).Based on the optimization model of theoretical reliability evaluation, the concept and index system of life-cycle reliability are proposed in this paper. Cost-benefit ratio method is proposed to optimize reliability improvement projects based on life-cycle reliability. Then, the reliability goal of whole system can be decomposed into individual business areas to refine reliability management. Finally, taking a coastal city as an example, the feasibility of the life-cycle reliability management method proposed in this paper is demonstrated, and the advantages and disadvantages of the method are summarized.