Most of the current distribution network evaluation index system is established for distribution network planning, and a complete index system to evaluate the operation state of distributed network hasn't been formed. A practical index system to evaluate the operation state of distributed network is established, which includes 6 upper indexes and 23 underlying individual indexes. The definition of every index, the basic data needed and its resources related to index calculation are introduced in detail. AHP-Delphi method is used to calculate the weight of every index in order to improve the objectivity of the index weights, and fuzzy membership function is adopted to determine the formula of every single index. Finally, the feasibility and effectiveness of the index system and method are verified through the comprehensive assessment of the operation state in a realistic distributed network.