This study compared two simplified methods for phytoplankton chlorophyll-a concentration measurement-the hot ethanol method which use 90% hot ethanol as the chlorophyll-a extraction agent and the cool acetone method which use 90% cool acetone as the chlorophyll-a extraction agent.The hot ethanol method is used widely in the wTorld now but the cool acetone method is normally used in China.The results show that the hot-ethanol method has more advantages than the cool-acetone method, which are faster and easier to handle, more complete extraction and lower toxic-There is significant statistical difference between these two methods.By using the formula Chla_ethaml=1.261 Chla_acetone-3.5, the cool-acetone method data can be transfered to the hot-ethanol method data.