This paper deals with the active wave control of a flexible beam using the wave filter constructed with four point sensors. It is the purpose of this paper to verify the active wave control system with adaptive feedforward technique. Firstly, the active sink method is introduced which is useful as a performance index of active wave control method. If the active sink system is constructed, all vibration modes are made inactive (more than suppressed), and its frequency characteristics are similar to the one of semi-infinite beam. Next, the design procedure of the wave filter using four point sensor is presented, its realization also being presented. Finally, experiment of the active wave feedforward control system is carried out, demonstrating the validity of the proposed method and the robustness against the sensor placement.