To compare phytoplankton communities dynamics and their relationships with environmental factors in reservoirs located at lower recheas of Yellow River, the differences in phytoplankton community structure between the two mountainous regions and the Yellow River Reservoir were studied. A survey of water quality and phytoplankton communities of two mountainous (Wohushan and Jinxiuchuan) reservoirs and two Yellow River (Quesha and Yuqingn) reservoirs was carried out from September 2012 to August 2013 in Jinan City. Totally, 51 species of phytoplankton were identified, composed mainly of Chlorophyta, Cyanobacteria and Diotam, with common species of Fragilaria Lyngbye, Planktonema, Cyclotella and Chlorella. Phytoplankton abundance ranged from 42×104 cells/L to 4566×104 cells/L in four reservoirs, and the seasonal differences were significant. The abundance of the phytoplankton in wet season was significantly higher than that in the other two periods, with Wohushan and Queshan Reservoirs significantly higher than other reservoirs. Statistical analysis suggested that the abundance of phytoplankton was limited by total phosphorus and water temperature in mountainous and Yellow River reservoirs, respectively. The differences in phytoplankton community structures between mountainous and Yellow River reservoirs was bound with water sources and types. Principal component analysis（PCA）of summarized data indicated that ion species, trophic states, TN∶TP ratios and water temperature were the most important factors influencing phytoplnakton community structure in moutainous and Yellow River reservoirs.