The water quality of Techeng Island Mangrove Nature Reserve was assessed using different models based on data from 2009 to 2010. Key pollutants were dissolved inorganic nitrogen, dissolved oxygen, oil, and dissolved inorganic phosphorus. Dissolved inorganic nitrogen was the most important pollutant, not meeting sea water quality standards. Overall, the water quality was lightly polluted, with high levels of organic pollution and eutrophication. The influence of Zhanjiang Harbor worsened the pollution in the area.