Abstract: The effects of light intensity, temperature and pH on photosynthetic characters of Haematococcus pluvialis CG-11 were studied by measuring photosynthetic O2 evolution and fluorescence kinetics. The results showed that the saturation thetic rate was obtained at 25℃; the photosynthetic efficiency kept quite high at the pH range of 7.5-8.0, with the maxi-range of 7.5-8.0, the Fv/Fm, Fv/Fo, ΦPSⅡ and ETR increased following the rising of pH, with their maximum values at pH 7.5, Fv/Fm and Fv/Fo decreased significantly over pH 7.5, while the decreasing trend didn't change obviously in ΦPSⅡ and ETR.