Abstract: With the continuous advancement of marine ecological civilization construction, the influence of coastal nuclear (fire) power plants on marine ecological environment has been paid more and more attention. This study investigated systematically the water quality of water intake and drainage, as well as 48 stations in the sea areas near the nuclear power project in Hainan from 2016 to 2017, and evaluated the effects of water intake and drainage from the nuclear power project on water quality. The results showed that in the year the project operated, water quality in the intake and outlet was good and met Class I or Class II seawater quality standards. No eutrophication was observed. The water quality was generally good in adjacent sea areas. Most indicators met Class I or Class II seawater quality standards. Slight eutrophication occurred in few stations due to industrial pollutant transport by monsoon and land-source nutrients discharge. This study found that the water quality of the sea area near the nuclear power project in Hainan was generally good, and the project has little influence on water quality.