During one year survey, a data set of phytoplankton community and environmental parameters in 20 sampling sites was analyzed in order to describe seasonal succession of phytoplankton community and its relationship with environmental variables in Qinhuangdao coastal areas of China by multivariate analysis. The population of phytoplankton community had significantvariation with seasonal succession, in which Aureococcus anophagefferens played an important role on the whole year. The trend of whole diversity index show the community structure became more stable in winter. The results ofprinciple component analysis (PCA) applied to the environmental factors indicated four major seasonal groups in environmental variables. We found one environmental factor influenced mainly on environment each season in addition to the complex of winter waterbody. The redundancy analysis (RDA) examined phytoplankton community structure and variation were mainly affected by the hydrological factors. Furthermore, this paper discussed the relationship between dominant species and the environment factors, and we inferred Chaetoceros decipiens as potential breakout of harmful algae blooms (HABs) by RDA ordination.