Electromigration effect is still a dominating failure mechanism of interconnect for deep-submicron and super deep-submicron scale. However, defect, which exists throughout IC manufacturing process, is another important factors affecting IC interconnection lifetime. When there is a defect on interconnection, this interconnection lifetime is shortened because of electromigration effect. In this paper, a new failure model of IC interconnection is proposed based on analysis of the available estimation models of IC interconnect lifetime. Many factors, such as the sizes of the defect, wire width, wire length and so on, are considered in this new model. The simulation results show that the model is valid.