Abstract: The optimal range of Fe³⁺ concentration for the growth of Haematococcus pluvialis CG-06 and the influences of Fe³⁺ on the photosynthesis of H.pluvialis were investigated by measuring optical density of algal culture,pigment changes,chlorophyll fluorescence and low temperature fluorescence spectrum.H.pluvialis CG-06 was grown in BBM media in batch culture and six Fe³⁺ concentrations(0,1.79,8.95,17.9,35.8,71.6 μmol·L^-1)were obtained by adding different amount of EDTA-FeNa(Ⅲ).The results showed that the optimum Fe³⁺ concentration for growth of H.pluvialis CG-06 was 8.95 μmol·L^-1.However,at relatively higher Fe³⁺ concentrations or Fe³⁺ concentration lower than 1.79 μmol·L^-1,algal growth could be inhibited.The data of Walz-PAM showed that the activity of PSⅡwas decreased significantly either at Fe³⁺-deficient condition or Fe³⁺-excessive condition and the number of open state reaction centers was reduced,resulting in inhibited photosynthesis.At either Fe³⁺-deficient condition or Fe³⁺-excessive condition,low temperature fluorescence emission spectrum showed that the peak at 710 nm was reduced while the peaks at 684 nm and 694 nm were enhanced,demonstrating that energy distribution between two photosystems was changed,with more energy being distributed to PSⅡ and consequently limi-ting the activity of PSⅠ.Under Fe³⁺-excessive condition,the fluorescence of PSⅡCP₄₇ decreased significantly,but that of PSⅡCP₄₃ increased relatively,which indicated that D₁ protein degradation might exist.