In the paper， influence of lose object defects on electromigration median-time-to-failure （MTF） for six-layer copper interconnect is investigated. The temperature model with defects for each interconnection layer and MTF model for defects in different interconnection layers are presented respectively. So， the defect influence on electromigration MTF of copper interconnect can be calculated quantitatively， and the method to increase MTF is also presented. The bigger the ratio of interconnect width to the effective interconnect width at the defects， the shorter the MTF， and higher temperature at defects can also shorten the MTF. When the parameters of interconnect wire vary greatly between different layers， the MTF is affected by the ratios and the temperature， and decreases rapidly. Based on the physical model， the temperature and the MTF of copper interconnect can be calculated accurately， which can guide IC design and manufacture effectively.