Abstract: To determine the seasonal changes on and the environmental factors that affected the bacterial community at Zuohai Lake in Fuzhou, a survey was conducted at 4 sampling sites on the lake from February to August in 2012. A genetic library of their 16S rRNA gene clones was established. Canonical correspondence analysis (CCA) was used to examine the correlation between the bacterial diversity and the environmental factors. The results indicated that β-Proteobacteria and Cyanobacteria were the predominate lineages in the water, followed by α-Proteobacteria, Bacteroidetes, and Actinobacteria. A significant seasonal variation in composition of the bacterial community was detected. Among various categories of bacteria,Cyanobacteria appeared most dominant in the spring and summer; while β-Proteobacteria, in the autumn and winter. The results of CCA showed that the bacterial community in the water was mainly affected by pH, chlorophyll a (Chla), transparency (SD), and total nitrogen (TN) in the spring; pH, Chla, SD, and total phosphate(TP), in the summer; TP, Chla, and TN in the fall; and, water temperature, pH, and SD, in the winter. Thus, in general, the bacterial growth in the lake closely related to the temperature as well as the nutrients available in the water.