Abstract: The stability of the sediment aggregation directly impact the erosion process of the Yellow River estuary coast zone. Some methods, including scanning electron microscope, soil physical and chemical analysis, were used to analyze and contrast the basic physical and chemical properties of the loess and the sediments in the Yellow River estuary. A study was implemented on the aggregate influence of calcium carbonate and Ca²⁺ on sediments of the Yellow River estuary by testing aggregation values under different conditions. The results demonstrate that calcium carbonate is the main material of sediment aggregation in the Yellow River estuary. The average calcium carbonate content is 10.67% that consists with Calcium carbonate content in loess. This indicates that calcium carbonate in the form of microcrystals aggregates fine particles, which are carried along the Yellow River and deposited in Yellow River estuary. There exists a tendency that calcium carbonate contents are higher in bigger size particles than in smaller ones. Calcium carbonate shows stronger aggregation than calcium ion. The clay particles in the Yellow River estuary are not basically dispersed and mainly exist in form of microaggregats because of the aggregation of calcium carbonate. This phenomenon is more obvious under the long-term effect of back and forth currents and waves.