Abstract: The experiments were carried out with the test method of exposure-recovery.The concentrations of 50% growth inhibition, algistatic response and algicidal response, three gradually increasing toxicity of Cu2+ on cells of Selenastrum capricornutum Printz, were 0.204, 0.297 and 0.316mg/l respectively, derived from regression equation between Cu2+ and specific growth rate corresponding with this concentration.It was shown that algal cells were damaged irreversibly when Cu2+ above algicidal concentration, and the re-sults of recovery experiments could evaluate the extent of cell damage in algal toxicity test.