Abstract: The trends of dissolved inorganic nitrogen and phosphorus in Shenzhen coastal waters during the past 30 years, as well as the frequency and areas of HABs were analysed, the correlationship between nutrients and HABs was also investigated.The results show that the nutrient level of the eastern waters was lower than that of the western, the eastern waters has not reached up eutrophication level, the western waters has been eutrophic or P-limiting potential eutrophication level in most of the years.There was the highest occurrence frequency of HABs in Dapeng bay and Shenzhen bay, the largest areas of HABs located in Shenzhen bay and Zhujiang estuary.Correlation analysis showed that dissolved inorganic nitrogen and phosphorus were no significant correlation with frequency and areas of HABs, but NH₄-N (Dapeng bay) and NO₃-N (Zhujiang estuary) were significant with frequency and areas of HABs.