Analysis of seismic response is very important to the seismic design of bridge. Based on theory of random vibration and response spectral method, the mean square root response of the internal forces of high-piers and long-span continuous rigid frame-beam bridge subjected to the stationary random seismic excitation and varying spatial seismic action was investigated. The conclusions showed that the analysis of random vibration is in accord with the response spectrum method excluding the spatial variation effect of the seismic action. The wave propagation effect and the coherence loss would surely change the internal forces of the continuous rigid frame-beam bridges and the computed conclusions by random vibration are greater than by response spectrum in most circumstance. The large differences of the site conditions of the bases significantly change the response of the continuous rigid frame-beam bridges, which should be included in the seismic design of the bridges.
