In order to study the effect of falling-still in dissipation of bottom flow,the paper studied the influence of falling-still on flow pattern, underflow velocity and fluctuating pressure based on a hydraulic model test from a project. Results show that when the flow is constant, the flow pattern in the dissipation basin would evolve from bottom flow to submerged admixture flow as well as surface flow with the increase of falling-still height.The falling-still can reduce the underflow velocity in first half of the stilling basin, and the higher the height of falling-still, the more the decrease of maximum underflow velocity; and in the second half of the stilling basin, the falling-still has hardly effect on underflow velocity. The falling-still also has a crucial influence on fluctuating pressure, with the increase of falling-still hieght, the maximum fluctuating pressure increases first and then decreases. Along the flow direction of stilling basin, the fluctuating pressure and the underflow velocity increase first and then decrease and the position of their maximum values is in the same region.