Based on the basic principles of dynamics, a simplified dynamic mechanical model with multiple degrees of freedom was established for an irregular bridge. The dynamic equation of the model was derived according to Lagrange's equations. Combined with Runge-Kutta method, the seismic behavior of irregular bridges under traveling wave excitation were studied using a self-compiled program, while considering the influence of some nonlinear factors, i.e., the bearings friction sliding and structural pounding. The results show that the combined action of traveling wave effect and pounding effect can increase the bending moment of short piers. The traveling wave excitation can increase the rubber bearing displacement, and the increase in peak displacement of the bearing above the last pier the seismic wave reaches is most obvious. Under the action of earthquake, the laminated rubber bearing above short piers is prone to slide; therefore, in anti-collision designs of irregular bridges, the traveling wave excitation and bearings friction sliding should be considered to find out the maximum pounding force of adjacent structures, in order to guide the design of irregular bridges.