Abstract: The simple and rapid method of direct determination of Cu(Ⅱ) in the seawater after cultured three planktonic microalgae was investigated with differential pulse anodic stripping voltammetry(DPASV).The concentration of Cu(Ⅱ) in the seawater containing exudates released from marine planktonic microalgae were measured by DPASV after acidification by nitric acid.The relative standard deviation was 1.6%～3.0% for determining four samples containing exudates of microalgae,which were not significant differences compared with that of samples of nitric acid digestion.The recovery ratios were from 90.1% to 119.2%.