Abstract: Based on aerial remote sensing data and field observation data, this paper analyzed the temporal-spatial characteristics of thermal discharge from Liaoning Hongyanhe Nuclear Power Plant in summer. The results show that: (1) The temperature retrieved from aerial remote sensing data are strongly correlated with the field observation temperature and thereby are reliable. (2) There is a similar spatial distribution of thermal discharge under the same tide state from spring to neap tide. (3) Water depth and tidal current are important factors affecting the diffusion range and direction of the thermal discharge high-temperature area. After the thermal discharge spreads offshore to a certain distance, the water velocity and depth are significantly higher than those nearshore area, which is conducive to the rapid mixing of thermal discharge with cold water, prompting the rapid diffusion of heat and a sharp drop in temperature. Meanwhile, the periodic variation of water velocity (flood and ebb tides) directly determines the diffusion direction of thermal discharge. (4) Aerial remote sensing monitoring by unmanned aerial vehicle can effectively compensate for the inherent limitations of temporal-spatial resolution of satellite remote sensing monitoring, while offering higher accuracy. It can be used as the core technical means for the dynamic monitoring of thermal discharge from nuclear power plant in the future.