Salinity is an important substances involved in the material cycle of lakes. Salinity increase in lakes poses a serious threat to the health of lake ecosystems. Lake Ulansuhai is one of the eight largest freshwater lakes in China, the largest lake in the Yellow River Basin, and also a typical shallow grassland lake in the cold and arid zone in Inner Mongolia. The lake water usually starts freezing in the early November and thawing in the end of March or in the early April of the following year. Total dissolved solids(TDS)and salinity in the lake have been increasing gradually and are at a high level at present. In order to reveal the distribution and migration characteristics of the TDS and salinity in the ice-water-sediment interface, samples of the ice, water, and sediments at different depths were collected at seven sampling sites during the ice-sealing period. The concentrations of TDS, Na⁺ and Cl^- were analyzed. The distribution coefficient (K) of TDS, Na⁺ and Cl^- between the ice and water were analyzed. The diffusion fluxes of Na⁺ and Cl^- between the water-sediment interfaces were estimated. The results showed that the mean K of TDS, Na⁺, and Cl^- were 0.02, 0.03 and 0.01, respectively. This indicated that the salinity was gradually concentrated in the water body during the process of ice crystal precipitation. As a result, the salinity would be further transported into sediment due to the concentration gradient between the water-sediment interfaces. The estimated mean diffusion fluxes of Na⁺ and Cl^- between the water-sediment interfaces were -229 mg/(m²·d) and -676 mg/(m²·d), respectively. In short, during the lake's freezing process, the salinity migrated to the liquid phase due to the precipitation of ice crystals. The concentration of salinity in the water body increased gradually and then migrated into sediment. This would constitute a stress on the lake's ecological environment.