Abstract: In this paper a numerical simulation for intake water temperature and aquatic environment temperature field of cooling water system for the thermal power plant under the action of tide motion by using the hybrid method of fractional steps with L_∞-stability^[5] is given, and its hydro-thermal behavior and environment pollution are predicted. The computed elevation of water and velocity field are in good agreement with the prototype observations, and the average intake water temperature and aquatic environment temperature distribution are also in consistent very well with the laboratory experiments.