Shilianghe Reservoir is the largest artificial lake in Jiangsu Province. It is very important to study the sedimentary rates of the reservoir in order to understand the environmental change in the river basin. ¹³⁷Cs technique is used to date a sediment core collected from Shilianghe Reservoir. Two distinct ¹³⁷Cs peaks are identified in the core, which are ascribed to the abundant fallouts occurring in 1963 and 1986. The grain size analysis indicates that clayey silt and silty clay are the main sedimentary types with a trend of gradually fining from the bottom to the top, and revealed a heavy rainfall event in 1970. Sedimentary rates of the core can be divided into several distinctive stages:10.85 cm/a from 1963 to 1970, 3.81 cm/a from 1970 to 1986, and 1.32 cm/a from 1986 to 2005. Furthermore, the environment significances were explained by using the sedimentary records. Through the comparison between grain size characteristics and historical precipitation records, the changes of coarse sediments contents and rainfall are of the similar trend, which directly reflects the information such as the intensities of rainfall and hydrodynamic transportation. Sedimentary environment of the Shilianghe Reservoir is typical deltaic under the controls of runoff and sediment transport, variations of water level and local terrain. Therefore, sedimentary rates are becoming low gradually following the general law of reservoir siltation. Furthermore, human activities have influenced the changes of sedimentary rates, such as construction of large reservoirs in the upstream of the river.