This study compared the 4 methods for phytoplankton chlorophyll -a concentration measurement, i.e. the hot ethanol extraction method, acetone extraction method, BBE fluoroprobe instrumental method and YSI 6600 instrumental method. The hot ethanol extraction method is used widely in the world now and the acetone extraction method is normally used in China．The study results show that there is a good comparability on measurement results between ethanol extraction method and the BBE fluoroprobe instrumental method. The concentration value level may be overestimated by the acetone extraction method. Some difference of results may be existed between the YSI 6600 instrumental method and hot ethanol extraction method. The results of BBE fluoroprobe instrumental method can be partially adopted. The results of YSI 6600 instrumental method can be used as a reference value of the experiment. The omission of centrifugation in the acetone extraction method caused some differences to the results.