Abstract: Low-temperature water cooling is an effective means to solve the energy consumption problem of data centers, but its environmental influence of the generated thermal drainage cannot be ignored.Take Wudang cloud valley big data center as an example, based on the MIKE21FM software, a two-dimensional numerical simulation model from Danjiangkou Reservoir Dam to Huangjiagang Hydrological Station was established, and the influence of different locations of the cooling water outlet of the data center cooling system on the diffusion law of thermal discharge was studied.The results showed that with the increasing of water depth and flow velocity at outlet, the maximum temperature rise of the thermal discharge and the corresponding temperature mixing zone gradually decrease.When the water depth exceeds2m, the local maximum temperature rise is less than1℃.The research results can provide reference for the site selection of the data center cooling water outlet and the analysis on influence of thermal discharge using low temperature reservoir water as the cooling water source.