For high-speed operation of electric railway, the contact loss of the pantograph is one of the most important subjects. Through theoretical analyses and fundamental experiments, it is confirmed that the magnitude of the contact force fluctuation is proportional to the vertical velocity amplitude of the incident wave to the pantograph. In order to investigate the influence of the wave motion in a practical catenary-pantograph system, laboratory running experiments and field test on a Shinkansen line are carried out. From the results thereof, it is found that the backward wave incident to the pantograph is much more influential that the forward wave, and that the influence of the wave motion on the contact force fluctuation is comparatively large. A hanger developed to have a spring and damping mechanism is found to effectively reduce the wave motion of the contact wire incident ot the pantograph and decreasing the contact loss ratio. It is expected that damping catenary vibration will contribute to speed-up in electric railway.