To distinct the impacts of climate changes and dam constructions on water temperature, changes of water temperature in the Jinsha River mainstream over the past 50 years are studied based on the temperatures daily observed at Batang, Shigu and Huatan hydrological stations, using the methods of regression analysis and wavelet analysis.The results show that the water temperature in the Jinsha River mainstream increased downstream along the river and changed at different scales of 1-year, 4-to 6-year and 10-to 12-year.The average annual water temperatures at the selected three stations increased at the rate of 0.0063-0.0170 ℃/year, which is regarded as the contribution of climate changes. However, dam constructions on a branch exerted an obvious impact on the monthly variation in water temperature at the Huatan station.During the warming periods, the temperatures became lower than that before the dam constructions and the reduction magnitude reached the maximum by as much as 0.8℃in April.During the cooling periods, the temperatures were higher than that before the dam constructions and the increase magnitude reached the maximum by as much as 0.8℃in December.