The most important method of understanding liquefaction-induced engineering failures comes from the investigation and analysis of earthquake damage. In May 2021, the Maduo M_s7.4 earthquake occurred on the Tibetan Plateau of China. The most representative engineering disaster caused by this earthquake was bridge damage on liquefied sites. In this study, the mutual relationships between the anti-liquefaction pre-design situation, the ground motion intensity, the site liquefaction severity, and the bridge damage state for this earthquake were systematically analyzed for typical bridge damage on the liquefied sites. Using field survey data and the current Chinese industry code, simulations of the liquefaction scenarios at typical bridge sites were performed for the pre-design seismic ground motion before the earthquake and the seismic ground motion during the earthquake. By combining these results with post-earthquake investigation results, the reason for the serious bridge damage resulting from this earthquake is revealed, and the necessary conditions for avoiding serious seismic damage to bridges built in liquefiable sites is presented.