The effects of iron and EDTA on the growth of Chlorella sp. KR-1, a highly$CO_2$tolerant fresh water micro alga, have been determined. The algal growth was significantly affected not only by iron concentrations in the medium but by the ratio of iron to EDTA. The linear growth rate and the final cell concentration are increased with the supplementation of EDTA. Enhanced growth of Chlorella sp. KR-1 by the supplementation of EDTA was mainly due to the fact that the supply of iron to the algal culture had been possible for a longer time. When Chlorella sp. KR-1 is cultured in the medium of iron-15H-EDTA, the linear growth rate and the final cell concentration are at their maximum, 0.88 g/l${cdot}$day and 9.1 g/l, respectively. The results show that Chlorella sp. KR-1 may be used for mass cultivation to fix$CO_2$from stack gases.