Abstract: The Wudongde Reservoir is a seasonal regulating reservoir in Southwestern China, and the reservoir water temperature structure was projected by the laterally averaged 2D reservoir water temperature model. The result shows that the water temperature structure of the reservoir presents seasonal stratification characteristics. The reservoir operation has affected on the dam downstream water temperatures, which included low-temperature water discharge in spring and high-temperature water discharge in winter. Compared to the natural river conditions, lower temperature water can be discharged between February and August while the water intake scheme of single layer was adopted. The maximum downstream water temperature decline could be 2℃, and the low-temperature waters had produced opposite effects on fish reproductions. Stop-log intake works will be taken in the Wudongde Hydropower Station during the fish spawning period between March and June annually, because the fishes are sensitive to low-temperature waters. Compared to the water intake scheme for single layer, the stop-log intake works showed notable improvements on downstream water temperature changes. The discharged water temperature can be increased by 0.8～1.1℃，which can slow down the water temperature delaying effects.