A phytoplanktonic investigation of Tanjiang River was conducted in March 2011. 202 species of phytoplankton belonging to 86 genera and 7 phyla were identified altogether. Chlorphyta and Bacillariophyta which occupied 36.14% and 43.56% of the total number were the most, indicating that the green algae and diatom were the dominant group. Tanjiang River was β-meso-polluted to oligo-polluted judging from phytoplankton community while it was clean or light-polluted judging from Shannon-Weaver diversity index, Margalef diversity index and Pielou evenness index. Tanjiang River was light-polluted or oligo-polluted judging from the above indicators in normal water season, but there has been a trend to β-meso-polluted.