Based on 24 cruises at 15 stations from January 2009 to December 2010, interannual variations in the phytoplankton community and their relationship with other environmental factors in the Jincheng area of Laizhou Bay were studied. Phytoplankton were vertically hauled using a type-Ⅲ standing phytoplankton net and environmental factors were recorded in situ synchronously. A total of 81 species of phytoplankton belonging to 43 genera of 4 phyla were detected. Bacillariophyta and Pyrrophyta were dominant, accounting for 67 and 11 species reflecting 82.7% and 13.6% of the total taxa, respectively. Xanthophyta included 2 species, while Chrysophyta included 1 species, accounting for 2.5% and 1.2%, respectively. Both in 2009 and 2010, the phytoplankton species composition and proportion were very similar. Compared to 2009, the proportion of diatom showed a slight increase, while dinoflagellates decreased slightly in 2010. Leptocylindrus danicus, Pseudo-nitzschia pungens, Skeletonema costatum, Chaetoceros curvisetus, and Chaetoceros lorenzianus were the most abundant species in Bacillariophyta, while Noctiluca scintillans was most abundant in Pyrrophyta. Interannual variability of phytoplankton abundance and the number of species showed a clear bimodal distribution. In 2009 and 2010, the average cell abundance was 465×10⁴ (38.4×10⁴-1351×10⁴) and 457×10⁴ (41.8×10⁴-1380×10⁴) cells/m³ respectively, all of which were lower than the average values observed in 1982-1983. CUSTER and MDS ordination analyses showed that the phytoplankton community was divided into four groups at 60% similarity. Group I contained samples from May, in which Noctiluca scintillans and Chaetoceros lorenzianus were the most abundant species. Samples from November through April belonged to Group Ⅱ, in which Skeletonema costatum, Chaetoceros curvisetus, and Noctiluca scintillans were the most abundant species. Group Ⅲ included samples in August, September, and October, in which Chaetoceros lorenzianus and Leptocylindrus danicus were the most abundant species. Group IV included samples from June and July, in which Chaetoceros lorenzianus and Pseudo-nitzschia pungens were the most abundant species. The means of the Shannon-Winner diversity index, Margalef richness, and Pielou evenness were 2.715 (1.446-3.807), 2.418 (1.545-3.153), and 0.523 (0.263-0.706), respectively. Both the diversity index and evenness of phytoplankton reached a maximum in March and October, while the minimum value was observed in July. The minimum value of the evenness index of phytoplankton was detected in June to September. Water temperature and salinity were the main environmental factors affecting the community structure of phytoplankton. Water temperature showed significantly positive correlations with Chaetoceros lorenzianus (R=0.613, P<0.01), but negatively correlated with Chaetoceros curvisetus, Skeletonema costatum, and Noctiluca scintillans (R=-0.662, -0.649, -0.649, P<0.01). There were negative correlations between the chemical oxygen demand and Chaetoceros curvisetus and Skeletonema costatum (R=-0.589, -0.480, P<0.05). Salinity was significantly negatively correlated with Skeletonema costatum (R=-0.585, P<0.01), whereas other environmental factors were not significantly correlated with the abundance of dominant species.