For sketchily illustrating the travel waves of transverse or longitudinal wave of different length, the process of forming wave, the propagation of wave, addition of waves, the standing waves reflection of wave, superposition of wave and damping of wave. It also can measure the velocity of wave and observe clearly the transverse and longitudinal stationary wave; the waves travel slowly so that they can be observed directly and distinctively. It is suitable for demonstration in colleges and middle schools.