Due to the increasingly serious ecological degradation of offshore systems, the study on offshore water quality health has attracted more and more attention of the researchers and decision-makers. In this paper, water quality health assessment of offshore area in north branch of the Yangtze River Estuary from July 2006 to January 2007 was studied by fuzzy comprehensive evaluation method. The water quality health conditions of this offshore region were assessed by the use of 6 measuring sites, with DO, TN, TP, petroleum, inorganic nitrogen and active phosphate indicators. Based on the comprehensive assessment, the assessed results are categorized into 4 "very healthy", "healthy" and 2 "unhealthy" statuses.