In order to investigate the influence of thermal discharge on water temperature of the Yangtze River in Anhui Province, a three-dimensional hydrodynamic temperature transport model for Anqing -Wuhu reach of the Yangtze River main stream was developed. Parameters of the model were calibrated and verified according to the measured hydrological data. The influence scope and extent of two kinds of discharge conditions (before and after the discharge reduction) on the surrounding water temperature under adverse conditions were predicted for transverse section and longitudinal section respectively. The results showed that under the two discharge conditions, the targeted water temperature had not been affected, the distribution of water temperature increment presented an obvious vertical variation, and the impact degree gradually decreased with the increase of the water depth. The thermal pollution zones of transverse section and longitudinal section generated after the discharge reduction were both smaller than those generated before the reduction. The maximum length of thermal pollution zone was 1.074 km, and the maximum temperature increment was 0.343 ℃ before discharge reduction. Comparatively, the maximum length of thermal pollution zone was 1.006 km and the maximum temperature increment was 0.321 ℃ after the reduction. The prediction results can provide some guidance for regional water ecological protection.