The existing assessment system for distribution network is not suitable to the individual project, it is more applicable to the traditional power grid or focuses more on the assessment of power grid technology performance. The first-class distribution network is the development goal of Chinese electric power enterprise. According to the life-cycle of the distribution network project, this paper establishes an index system by carefully selecting index from the aspects of planning, design, construction and operation, and builds a sub-index system which is suitable to the distribution network annual overall assessment and the individual project assessment from four dimensions i.e. implementation process, power grid performance, environmental and social impact, and investment benefit. It sets weight by combination of the expert method and information entropy, conducts the overall assessment for annual investment by using the macroscopic index and for individual project by using the microcosmic index, and establishes index membership grade function by referencing international advanced distribution network index. The system has been applied to assess the annual investment of the distribution network of a city in southern Jiangsu successfully. This work is supported by National Natural Science Foundation of China (No. 51105344).