In order to understand eutrophication levels and characteristics of phytoplankton distribution in Changtan Reservoir in Meizhou City,Guangdong Province,and provide scientific basis for controlling of algae bloom,physico-chemical data,phytoplankton species and densities were determined from October 2011 to July 2012 from 10 sampling sites in Changtan Reservoir.The status of water pollution was evaluated based on trophic level index,Shannon-Wiener index,and analysis characteristics of phytoplankton distribution in Changtan Reservoir.The results showed that the Changtan Reservoir was at middle eutrophication level characterized in April,October and December,and high eutrophication level with downward trend from upstream to the reservoir in July.A total of 16 phytoplankton species have been identified,which belong to 4 phyla and 11 families,among which cyanobacteria and green alga were predominant with obvious seasonal succession.The density of phytoplankton ranged from high to low in order of the following months: July >April >October >December.Shannon-Wiener index value analysis showed that water pollution level was medium for the reservoir water body,and light in the upstream and reservoir catchment area (except July);this is consistent with the trophic level index values.The pollution source survey showed that nitrogen and phosphorus were the main pollutant indices of Changtan Reservoir,and mainly from livestock breeding wastewater.