Abstract: The Three Gorges Reservoir has changed the water temperature trend on downstream waters of the Yangtze River and has an important impact on downstream ecological environment. Based on the measured data of the Yichang hydrological station on Yangtze River during a period of 14 years(2000-2013), the one-dimensional longitudinal temperature model was used to analyze the temporal and spatial variation of water temperatures of the expanse of 300 km along the river, from Yichang to Jianli, which occurred as a result of the Three Gorges Reservoir Reservoir. The impact on spawning grounds due to water temperature variation was also discussed in different impoundments. The research results show the following:① As a result of the Three Georges Reservoir, there was a phenomena of planarization and delay of the water temperature process in Yichang. It is also evident that the discharged water is of a lower temperature during the summer and higher temperature in winter on downstream. Compared with the natural water temperature, the water temperature in Yichang changed to -4.3℃ in April and 3.7℃ in December during the period of the 175 m stage. ② As a result of the operation of this project, the water-air heat exchange on downstream river waters has also experienced much change, and the relatively strong flow has caused the water temperature of the nature status along the river to recover slowly. The dam also plays a decisive role in regulating the downstream water temperature. The water temperature of Jianli changed -3.2℃ and 3.0℃ in April and December respectively. ③ After the Three Gorges Reservoir was put into operation, the original water temperature in the Chinese sturgeon spawning grounds of Yichang which reached 20.0℃ in winter began to experience a delay of 10-40 days. The water temperature of 18.0℃ in the Four Major Chinese Carps grounds of Jianli in spring time also experienced a delay of 10-30 days. In accordance with the rising level of Three Gorges Reservoir, the trend of the delay will be more significant.