Abstract: During post-earthquake reconstruction, bridges and other key infrastructures should be quickly repaired or reconstructed for travel demand. During construction, integrated structural system of a bridge has not formed yet and aftershocks occurred at a high frequency in a short time, which would threaten the security of the structures. By the statistical results of aftershock occurrence in the early stage after the main shock, the current study regressed the probabilistic model of aftershock occurrence, which is based on the Probabilistic Seismic Hazard Analysis (PSHA), and proposed a fragility index in the process of the bridge construction and considered the calculation model of fragility in construction process. Take Wenchuan earthquake as an example. By analyzing the fragility of high piers in a mountainous area during the whole construction, it is shown that cracking damage easily occurs during the bridge construction in aftershock area and can affect the durability of the structure. Therefore, it is necessary to make a special assessment on the risk of earthquake damage to bridges under construction after strong shocks.