The construction and operation of the cascade reservoir group in the lower reaches of the Jinsha River has changed the water temperature characteristics of the original river. The temperature process of the water discharged by the power station has been smoothed and delayed, which has affected the proliferation and breeding of fish downstream.The inflow of downstream tributaries has a certain mitigating effect the flattening and delay effects of the discharge water temperature caused by the operation of the cascade reservoirs. This study analyzes the water temperature change patterns of the Jinsha River main stream and the Yangtze River main stream before and after the Minjiang River enters the confluence from May 2024 to April 2025, uses regression analysis to establish a target water temperature equation, and comprehensively analyzes the impact of various environmental factors on water temperature using statistical analysis, sensitivity analysis, and other methods. At the same time, it combines the actual dispatch operation simulation of Xiangjiaba Hydropower Station to carry out the water temperature improvement dispatch process. The results show that the inflow of the tributary Minjiang River has a certain mitigating effect on the water temperature flattening and delay effects in the study area; changes in the flow rate and water temperature of the main and tributary rivers will have an impact on the water temperature after blending, and at the same change range, the water temperature changes in the main and tributary rivers have a greater impact on the water temperature after blending and have obvious time characteristics; it is feasible to regulate the critical water temperature for fish spawning in the protected area by adjusting the outflow flow from the Xiangjiaba Hydropower Station, but the scheduling effect is limited.