To conduct a vulnerability analysis of bridges under seismic action in scouring conditions, the primary task is to analyze the hydrological data of bridge sites for hundred-year events, determine the distribution of scouring depth during the design reference period, and based on this specific distribution, select representative scouring depth values to carry out seismic vulnerability analysis of bridge structures under these values. Determine the failure probability under different scouring depths, establish the nonlinear relationship between scouring depth and reliability index, and based on the scouring depth distribution function, analyze the average failure probability of the structure under the combined action of scouring and earthquake. The scouring depth corresponding to this failure probability is the rational scouring depth based on risk analysis. Calculate the design scouring depth of the pile foundation in accordance with the hydrological report. The ratio of the aforementioned rational scouring depth to the design scouring depth is the combined partial factor of scouring action under the combined design condition of scouring and seismic actions.