In order to identify vulnerable lines in distribution network, this paper proposes a new model of comprehensive vulnerability assessment based on network structure importance and potential hazard vulnerability. On one hand, this model defines network structure importance of the distribution line by combining basic parameters of the complex network theory and the characteristics of the distribution network. On the other hand, the potential hazard vulnerability indexes of the distribution line are defined according to the severity of the impact on safety operation caused by load shock and fault disconnection. The weight coefficient of each index is calculated by analytic hierarchy process, which reflects the line vulnerability comprehensively. The rationality and effectiveness of this comprehensive vulnerability assessment model are verified by simulation results of IEEE 33-bus distribution system. This work is supported by Science and Technology Project of Guangdong Power Grid Corporation (No. GDKJXM20161884).