This paper analysed the existence of long-chain alkenones from the surface sediments in the Lake Qinghai and lakes in Qaidam Basin. The ratios of C₃₇to C₃₈alkenone is observed larger than 1 in both freshwater and saline lakes, while less than 1 in salt lakes. The calculated temperatures based on U ^K'₃₇ equation reported in literatures can fall within the observed temperature ranges for the Lake Qinghai, but are lower than air temperatures observed for lakes in the Qaidam Basin. The abundances of the long-chain alkenones in the saline lakes are found higher than those in freshwater and salt lakes, with the highest abundance of 86.09g/L in Lake Gahai with salinity of 103.2g/L. Such characteristics suggest that the algal precursors might prefer to live in water bodies with intermediate salinity but do not grow well either in freshwater or salt lakes. Thus the fluctuation of long-chain alkenone abundance might indicate variations of freshwater or saline environments.