Effects of GA and IAA on the respiratory and photosynthetic activity of each growth stage during the synchronous culture of Chlorella ellipsodiea, were investigated. 1) GA ($2{ imes}10^{-8}M$) affected most insignificantly on the respiratory activity of the stages Dn, Da, $L_1$, $L_2$, $L_3$-cells but only at $L_4$-cells treated with IAA($10^{-3}/M$) were promoted and $L_3$, $L_4$-cells were suppressed. With the treatment of GA-IAA the effects on respiration of eah stage cells were antagonistic. 2) Photosynthetic activity treated with GA during the each stage of Chlorella cells was promoted and IAA treated-cell were suppressed. The effect of GA-IAA upon the process of life cycle was also antagonistic. 3) It was revealed that respiratory and photosynthetic activity of Chlorella cells by the treatment of GA(($2{ imes}10^{-8}M$) and IAA($10{ imes}^{-3}/M$) had antogonistic effects.