Abstract: In recent years, much attention has been paid to mangrove conservation, but research on the effects of the thermal discharge from nuclear power plants on mangrove community characteristics is scarce, with most studies limited to simulating the effects of temperature extremes on mangrove plant growth and physiological characteristics under laboratory conditions. In this paper, the mangroves in the temperature rise area of the Qinzhou power plant were used as a reference system, and the mangrove community characteristics in the temperature rise area of the Fangchenggang nuclear power plant were analysed and predicted, which can lay the foundation for subsequent studies on the evaluation of the impact of coastal power plants on mangroves and provide guidance for related research.The results of the study show that: (1) the mangrove plant species and community types in the two forest areas are similar, and the direction of development is the same in that the mangrove tree or white bone loam is used as a community building species and gradually evolves towards the autumn eggplant community; the mangrove community diversity indices are low and the range of change is similar, and there is no significant difference in the four types of diversity indices between the two forest areas. (2) The comparison of the same community types in different areas and different temperature rise zones shows that the mangrove communities in higher temperature rise zones are more stable in structure and have better community characteristics; the temperature rise has no obvious adverse effect on affecting the community characteristics of the forest area. (3) The comparison of historical and current community data in the local forest area showed that three samples are in the range of 2 ℃−4 ℃ temperature rise zone,, but the community species composition, dominant species and community types in all three sites remained stable, and the community density and average plant height generally showed an increasing trend. There was no significant negative impact on the mangrove communities in this area due to warm water drainage or the naturally induced 2 ℃−4 ℃ temperature rise. In summary, this study shows that the warm water drainage from units 5 and 6 of the Hongsha nuclear power plant will not have an unacceptable impact on the mangrove ecology within the 1 ℃ temperature rise line.