Abstract: The water diversion project in Central Yunnan mainly transports water through tunnels and recharges 16 reservoirs along the line. In this paper,the water temperature variation along the water conveyance tunnel was analyzed by the method of analog measurement and the CE-QUAL-W2 model to study the vertical distribution characteristics of water temperature in Jiulongdian Reservoir. The main conclusions were as follows: the increase rate of water temperature along the tunnel was-0. 055℃/100 km,and the temperature drop of the whole section of the water conveyance main canal was calculated to be 0. 4℃ after water diversion and storage in Central Yunnan. Jiulongdian Reservoir is a seasonal water temperature stratification reservoir,in which the water temperature stratification occurs from March to August,and the maximum temperature difference between the surface layer and the bottom layer is 5. 2℃ in May. Due to the effects of low temperature and stratification of water temperature from theShigu water source,the discharge water temperature of reservoir is lower than that of natural water temperature from February to June in normal year,which decreases by 0. 3 ～ 2. 7℃ ． The maximum water temperature of the reservoir is0. 8℃ lower than before. It could be seen that the water diversion and storage in Central Yunnan has little effect on the discharge water temperature of Jiulongdian Reservoir. The irrigation water temperature in the tillering and growing stages of rice in the irrigation area is within the normal water temperature range of rice growing.