Based on the local movable bed conceptual flume tests, the longitudinal, transverse and vertical turbulent intensity distribution near the float cofferdam’s side during descending is presented using a Micro Acoustic-Doppler Velocimeter (MicroADV) to measure the instantaneous velocity. The turbulent width influenced by the changing of cofferdam subsidence depth, approaching flow velocity, upper flow depth is researched. The result shows that under the experimental conditions, the turbulent width influenced by the floating cofferdam subsidence depth is conspicuous, and by the approaching flow velocity, the upper flow depth is small relatively. In the experiment range, the relative turbulent width of D/B is increased with the floating cofferdam into relatively water depth Hc/H0 when the floating cofferdam acts alone. They are substantially linear relationship.