Based on monitoring data of air temperature, water temperature and Chlorophyll-a(Chl.a)in Lake Chaohu from March to June in 2007, the relationship between air temperature, water temperature and Chl.a concentration were analyzed using statisti-cal methods.The results showed that:The daily determination coefficient of determination of quadratic polynomial fit between Ta and Tw was the highest(0.81).The hourly coefficients of determination between Tw and Chl.a concentrations varied in a wide range(0 0.91), and their mean value was 0.35.The correlation between daily Tw and Chl.a concentrations was higher than that of the hourly data.Furthermore, the correlation between Chl.a and cumulative water temperature of some single day was very high in the eastern part of Lake Chaohu while the correlation was low in western part of the Lake Chaohu.However, correlation between day-to-day Chl.a and water temperature was much better in the WCL than that in the ECL.