This paper aims to discuss the characteristics of velocity field of the partial clapotis, based on the laboratry experiments and a newly developed third order theory. As the relative water depth decreases and the wave steepness increases, the crest of the time history of horizontal velocities is steepned and its trough is flattened, while the wave form bends forward in vertical velocities. In addition, as the left-lettlection coeffient is more than 0.8, the second harmonic component wave appears to be prominent in water surface profiles and vertical velocities at the node.
