Abstract: In order to explore stratification structures of water temperature in front of large reservoir dams and evolution laws of discharged water temperature in downstream river channels, and provide support and basis for reservoir management and optimal operation, taking Tingzikou Reservoir as the research object, high-frequency prototype observation of water temperature in front of reservoir dam and discharge water temperature was carried out from 2021 to 2023.The results showed that: ① Tingzikou Reservoir was a seasonally stratified reservoir, the stratification phenomenon was the most obvious in summer and the weakest in winter, and double thermocline was observed from July to September.The dramatic increase in inflow in the fall of 2021 enhanced vertical mixing of the water column and significantly disrupted the thermal stratification structure of the water layer.② The diurnal amplitude of surface water temperature was mainly influenced by air temperature, while the diurnal amplitude of water temperature in the deeper water layer was mainly influenced by thermocline internal waves.The location of the maximum daily variability was shifted to deeper water due to thermocline internal waves caused by daily regulation of outflow.③ The depth of the thermocline varied seasonally, and the trend of the thermocline thickness changes was opposite to depth of thermocline.Surface water temperature showed a significant positive correlation with SI.④ After the construction of Tingzikou Reservoir, the temperature of the discharged water and the downstream water temperature of Cangxi Station showed a significant warm-lag effect in May and cold-lag effect in October to February in next year.The water temperature at Cangxi Station lagged behind the air temperature change by about 44 days, and the time of arriving at the characteristic water temperature of 18 ℃ was delayed by 16 days compared with the natural process.The Cangxi navigation and hydropower project slowed down the outflow of Tingzikou Reservoir, which had a positive effect on the water temperature recovery of the downstream river.The results of the study can provide support and basis for optimizing reservoir operation and stratified water intake measures.