A fresh water microalga, which has tolerance to high concentrations of CO2, was isolated. The KR-1 strain was identified as a genus Chlorella. Though Chlorella KR-1 showed maximum growth at 10% (v/v) CO2, the strain showed a good growth rate up to 50% (v/v) CO2. The results indicated the feasibility of the KR-1 strain for massive cultivation using condensed stack gases.