To systematically evaluate the role of flow straightening screen as a physical algal control method in improving local water flow, thermal stratification, and regional water environment in reservoirs, a study was conducted on the Langhe Bay of Danjiangkou Reservoir. Using field experiments and numerical simulations, the effects of different flow deflection curtain schemes on hydrodynamics and water temperature stratification were analyzed. The results show that there is a significant stratification and density current at the end of the return water area of the Langhe River. The low-temperature water entering the upstream flows out of the bay in the form of bottom slope density current, while the downstream backflow water flows upstream from the middle and upper layers, providing favorable conditions for improving water temperature stratification through hydraulic regulation of the flow straightening screen. The hydraulic control effect of the flow straightening screen on the target area is significant under different flow conditions. Compared to the surface flow straightening screen, the bottom flow straightening screen can enhance vertical mixing. The higher the screen, the more turbulent the flow field, the stronger the vertical mixing, and the more obvious the weakening of water temperature stratification. The bottom flow straightening screen can enhance local water mixing, increase the average flow velocity by 0.02 m/s after installation, reduce the average water temperature by 1.6℃, and reduce the surface chlorophyll concentration by more than 30%.