In order to make a quantitative comprehensive evaluation of the operation mode of the distribution network, this paper proposes a method which uses the economy of Lagrangian function to determine the weights of the evaluation indexes. This method uses Lagrangian function to establish the quantitative comprehensive evaluation model which uses the security, quality, economy and environmental protection indexes as the constraints, uses different objective functions according to different demand, and is based on an united dimension. Then the comprehensive quantitative evaluation index system is discussed in the paper, and the obtained mathematical model is solved using interior point method. The result of a numerical example proves that this method can make evaluation of the operation mode of the distribution network, which proves the effectiveness and rationality of the method.#$NLKeywords: distribution network; operation mode; lagrangian function; comprehensive quantitative evaluation