To suppress the flexible vibration of railway vehicle carbody, a passive control method by mounting dampers longitudinally on the under frame of the carbody is proposed in this work. The influences of the dampers on the carbody flexible vibration reduction are firstly investigated by means of Green function. Then the effectiveness of the method is further verified by a nonlinear full-scale vehicle dynamic model. The results indicate that the proposed control method has good performance in suppression of the carbody flexible vibration.