The damages in the bridges severely endangered their lives. In order to ensure the safety and facilitate daily maintenance, the methods for detecting damages were needed. Conventional damage identification methods based on finite model updating achieved in precisely damage detection. However, their processes of finite element updating would cost a lot of computing time. Also, the finite element updating methods require multi-order modes of the bridges, which are difficult to obtain in actual scenes with regular traffic condition. Under such circumstances, this paper presented a bridge finite element updating method based on long-gauge strain response. This method utilizing long-gauge FBG sensors has two steps. The first step is to detect the location of the damage initially using a damage localizing method. Then in the second step, on the basis on step 1, the damage would be further determined through finite element updating through a multi scale element model to measure the location and extent of the damage more accurately. With the combination of step 1 and 2, the computation complex would be reduced greatly without harming the identification accuracy. In order to verify this method, an experiment was conducted in laboratory. In the experiment, the long-gauge strain response of the bridge models with a damage condition was extracted by the long-gauge FBG sensors mounted beneath them. Utilizing this method, the damage conditions can be successfully detected in the bridge model, which verified the potential of this method.