According to the 30a climatic data about 95 stations of Hunan Province from 1971 to 2000, and the data hour by hour about part of observation stations in Hunan from 2003 to 2004, this paper analyses Dongting Lake’s effect on temperature to surrounding areas and the whole province, the results show that: the yearly mea n temperature in the eastern part of the lake region shows a warm tongue. Dongti ng Lake changes the usually distribution trend of Hunan province that the temper ature in the south is higher than in the north, so that the monthly mean temperature in Hunan also shows distributions of East-West and transition. The lake district is the low-value areas of highest temperature, and the high-valu e of minimum temperature, daily range of temperature is lower. Compared to the s ame latitude and longitude regions of the province, and latitude of Hunan, the m onthly mean daily range of temperature in the lake district is lower, particular ly in the summer half year, in July it appears in the anti-phase, the temperatur e curve is more stable, and the daily maximum temperature appears 2 hours later, in the same weather conditions, the temperature amplitude of variation is alway s a little smaller, but under different weather conditions, the difference of th e daily maximum temperature and the difference of the daily minimum temperature are largest in sunny days, smaller in cloudy days and smallest in rain days.