This article made a temperature field analysis in a nearshore waters of a nuclear power plant in Fujian Province，and uses Landsat-8/9 TIRS thermal infrared satellite remote sensing data was used to study the temperature field distribution characteristics in different seasons before and after nuclear power operation. The research results show that the temperature inversion results of Landsat-8/9 TIRS data based on the radiative transfer equation algorithm have high reliability. Before the operation of nuclear power plants，there were significant differences in temperature field characteristics in different seasons in the sea area near the nuclear power plant site. In winter，the temperature field was generally more uniform，slightly higher in the south than in the north and slightly higher in the east than in the west. The water temperature near the water intake was slightly higher than that near the drainage outlet. The maximum temperature difference within 4 km of the plant site was about 1.5 ℃，and within 2 km was about 1.0 ℃. In summer，there was a large temperature difference in the region，showing the characteristics of being higher in the north and lower in the south，and higher in the west and lower in the east. The maximum temperature difference within 4 km of the plant site was about 5.5 ℃，and within 2km was about 2.5 ℃，and some parts were distributed in a disorderly manner. The water temperature near the drainage.After the operation of the nuclear power plant，the characteristics of the regional temperature field are basically the same as before，but there are obvious high-temperature bright spots at the drainage outlet，with a maximum temperature exceeding the surrounding area by 3.0 ℃. The intensity and area of the high-temperature bright spots in winter are greater than those in summer，indicating that the impact of thermal drainage discharge on the temperature field in the nearby sea area is stronger in winter than in summer.The flow direction of the current affects the local distribution of the temperature field，and the diffusion direction of the warm water discharge is related to the flow direction of the current. The Landsat-8/9 TIRS data basically meet the needs of regional temperature field distribution research，but it is difficult to realize the monitoring of full tidal temperature and drainage.