Abstract: The current comprehensive evaluation methods of voltage sags generally only consider the voltage sag level of the node, ignore the effect of the actual load of node connection and the importance of the load on the voltage sag evaluation results, and the description of the node voltage sag severity can not reflect the objective reality. In order to evaluate the effects of voltage sag events reasonably, considering the importance of load, a method for evaluating the severity of voltage sag considering the power grid side and the user side is proposed. First , the node voltage sag characteristics are obtained based on the fault positions method, and analytic hierarchy process is used to calculate the weight coefficient of voltage sag of different kinds of load. The power grid side index is determined by the node voltage sag characteristics and the influence coefficient of load. Then, according to the fault probability function of the sensitive equipment, the fault rate of the typical sensitive equipment is calculated as the user side index. Finally, the gray relational grade between the comparison sequence composed of evaluation indexes of nodes and reference sequence is calculated by using the grey relational analysis. The node sag severity is determined by comparing size of the gray relational grade of each node. This method is used to evaluate the voltage sags of a city network, and compared with the traditional evaluation method, the results show that the proposed method can reasonably modify the effect of load on the severity of the sag assessment, and the ranking of the node voltage sag severity is more realistic.