Abstract: By the means of experiment this paper probes into the shear stress of the static muddy water.The experiment indicates that the value of the static yield stress is larger than that measured from pressure capillary rheometer and increases with the resting time and the sediment content and is negatively proportion to the particle size.It is learned from the water channel conceptualized experiment that the a static shear stress produces the resistance of the hypoconcentrated laminar flow change with time, and this stress is the root of the globule siltation resulting in the cease of the whole hypoconcentrat ion muddy water flow near boundary of a channel and the root of natural barrier formtion.