Based on complex network theory， a complex network model of power systems is proposed using quasi-steady power transfer distribution factor（PTDF）， which can not only reflect the topological connection between components but also the actual power flow distribution. The component important can be analyzed with this model. Considering the efficiency for satisfying terminal load requirement of power systems， load loss rate is used to build the model of component vulnerability. The method of analyzing component vulnerability is presented with a program flowchart. Finally， results of IEEE case studies are used to verify the feasibility of the proposed model and the algorithm.