Abstract: To study the response of phytoplankton community to the water-sediment regulation in Yellow River in summer 2010, water samples were collected in the Yellow River estuary and its adjacent waters after the event.A total of 80 species (including 14 undetermined species) representing diatom, dinoflagellate, cyanobacteria, chrysophyte and chlorophytes were identified by microscopic analysis.Diatoms were dominant in all stations surveyed with 68 species identified and taking up 85% of the total phytoplankton.The main dominant species were Chaetoceros debili, Eucampia zodiacus and Ceratium furca in this survey. The changes of nutrients condition in the survey area affected the phytoplankton community structure significantly.This study provides fundamental information for further research about the influences of environmental changes on phytoplankton community in the Yellow River estuary and its adjacent area.