If it could be found that the relationship between early contact resistance of relay and lifetime, the lifetime of a single product would be obtained by the prediction of early contact resistance, instead of using the complete life tests. Meanwhile, this method could avoid the disadvantage of using the life of a batch of products to represent the life of a sample. So, the relationship between contact resistance values and lifetime in life tests are studied. Based on relays’ classification by the size of lifetime, the varying characteristic of the early contact resistance are compared and analyzed among groups of relays. The analysis shows that the lifetime of relays is related to the values of initial contact resistance. The relay is prone to early failure, and has short lifetime, when there are several large values of contact resistance in the early period in operation of relay, even if the value of contact resistant go back to the normal range after operating for a while. When the values of contact resistance are normal in the beginning period, and have a trend of soaring increase in the middle and later period, the relay is about to fail. The remaining useful life at the maximum of contact resistance is related to the change of the contact resistance values.