Acidleachable major elements (K, Na, Ca, Mg) of three riverine sediment cores have been measured. These cores were collected in Oct. 2006 from Daning River which is a major tributary of Yangtze River. The results suggest that the content of acidleachable major elements in the cores can reflect the characteristics and origin of the sediments. The average carbonate content in upper—middle Daning River is about 23%, which reflects limestone weathering in the Karst region; whereas the mean carbonate content is about 10% at the intersection of Yangtze and Daning River. This indicates a differently sedimentary origin from Daning River. After the construction of the Three Gorges' dam and 150mlevel storage of the reservoir, the water level in Daning River has raised rapidly. The deposition of the red clay which contains less carbonate around Shuanglong town strongly increased. As a result, the carbonate content and acidleachable major elements in the riverine sediments decreased sharply and the color of the sediment changed obviously. Since the first phase of the sluice of Three Gorges Reservoir in December 2004, the sediment thickness around Shuanglong town is about 11cm, which gives a sedimentary rate of 5.5cm/a in Daning River.