Gucheng Lake, a fresh shallow lake, and Daihai Lake, a brackish lake, are examplified to study the vertical distribution of organic carbon, total sulphur, and their ratio(OC/TS) in lake sediment, and their meanings in lake sedimental environment (climatic change in sedimental periods), palaeosalinity as well as environmental pollution. It is found that OC/TS decreases abruptly on the redox interface (5cm deep) of the sediment in Gucheng Lake, with high content sulphur and low carbon while increases when Daihai Lake was in its high lake level, and decreases in its low lake level corresponding with the sedimentary characteristics under the climate of cold-wet and cold-dry respectively. The Index (OC/TS) originally used in oceanic sedimentary research is shown in this paper the possibility of its application in limnological sedimentary research.