This thesis aimed to analyze the stable multimodal (3-peaked) particle size distributions (PSDs) of flocs in the Zhujiang River Estuary with the field observation data getting by LISST and the bottom boundary layer observation system during the dry season in 2010. The results show that the mean diameter of the basic building blocks of flocs, so-called primary particle, is about 8.3–9.0 μm; the mean diameter of microflocs in a range of 36–100 μm, and macroflocs have a size range of 180 μm to thousands of micrometers. In the neap tidal periods, the suspension sediment of halocline is dominated by the macroflocs with strong flocculation process; the mean diameter of flocs is increases and is controlled by flocs during the moderate and spring tide. The dynamic change of the tide has little impact on the multimodal PSDs and morphological parameters, with aggregation and breakage of the flocculation in the dynamic equilibrium. Study results further demonstrate the turbulent dynamic mechanism of flocculation by combining the turbulence data collected by the bottom tripod and the simplified Population Balance Equation (PBE). It is that, the high shear of the peak flow would enhance breakage of macroflocs to microflocs and decrease the mean diameter of flocs, on the contrary, aggregation is much stronger than breakage. It also shows that PSDs are in according with observation by solving PBE based on gaussian moment integral method. It turns out that PBE which containes the turbulent dynamic mechanism can be used to study the flocculation of cohesive sediment with turbulence and PSDs data.