Phytoplankton at inshore area of Laoshan and Liuqing River Bay of Qingdao were investigated in May and August, 2012. There were 36 species belonging to 23 genera of phytoplankton collected during the survey in May, and the total number of phytoplankton was 85.26×103～720.16×103cell/m3. An outbreak of Noctiluca scintillans was observed in May, when its cell number was more than 80% of the total cell count. The diversity index was influenced by N. scintillans, and the cell abundance was also low. In August, Fifty-four species belonging to 30 genera of phytoplankton were collected during the survey; the total number of phytoplankton was 43.00×103~1 116.27×103cell/m3. In August, phytoplankton was more diverse in survey areas, and the cell abundance was lower. Clustering analysis showed that the similarity of the phytoplankton community was more than 60% in May, and more than 50% in August. The cell abundance of phytoplankton at inshore area of Laoshan was more than that in Liuqing River Bay, while the diversity of the former was lower than the latter. Average cell abundance showed a negative correlation with N/P (r=-0.81, P<0.05), while the mean diversity showed a positive correlation with N/P (r=0.98, P<0.05). It is concluded that the key limiting factor affecting the cell abundance and diversity of phytoplankton was the inorganic nitrogen.