Abstract: Based on the net-phytoplankton data collected from Mindong coastal waters in summer from 2008 to 2017,a total of 4 phyla,8 category,including 263 species of phytoplankton were identified in recent 10 years,in which diatoms and dinoflagellates were the most dominant species,and 31.56% were red-tide species with potential risk,and the main principal phytoplankton ecotypes were eurythermy species.Interannual variability of species had great change,with the highest in 2017,and the lowest in 2012.The species cell abundances varied from 267.03×10⁴ to 44 379.31×10⁴ind/m³,while cell abundance of phytoplankton community depended on the cell abundance of diatom.Except 2008,the interannual variability of cell abundance showed bimodal type trend,with the highest in 2008,and the lowest in 2013.The distribution of phytoplankton abundance kept a trend of higher outside bay and lower inside bay,higher in the north coast and lower in the south coast,higher inshore and lower offshore.Skeletonema costatum, Chaetoceros curvisetus and Pseudo-nitzschia delicatissima were the common dominant species.The interannual variability of community diversity had great changes,with a sharp decline after the first rise,and then rise.The diversity level was low during the survey.The multiplaction of phytoplankton led to the low diversity level of phytoplankton,species inbalance,monotony of community,and appeared miniaturization phenomenon.Instead it showed that Mindong caostal waters was polluted by human disturbance.