To simulate the effect of the interactions of elevated temperature and weakened light in spring on the growth and photosynthetic capacity of Microcystis aeruginosa and Chlorella pyrenoidosa, an experiment was performed with these two strains at different temperatures (14, 16 and 18℃) and light intensities (100, 250 and 360mumol/(m~2·s). Growth curves were obtained by the results of cell counting with flow cytometry to reflect their growth trends. Photosynthetic capacity was measured by Phyto-PAM fluorometry. The results showed that the growth rate of M.aeruginosa reached its peak at the cell density of 2.99*10~6 cells/ml when the temperature was at 18℃ and light intensity was 100mumol/(m~2·s). At the same time, its photosynthetic capacity was much higher than other groups, and Fv/Fm values reached 0.39. While the growth rates of C.pyrenoidosa at the temperatures of 16 and 18℃ were similar, they were significantly higher than the growth rate at 14℃, and the photosynthetic capacity kept fluctuating throughout the experiment. Our results indicated that elevated temperature and weakened light promoted the growth and photosynthetic capacity of M.aeruginosa. Moreover, M.aeruginosa is much more likely to prefer low light intensity at high temperature than low temperature. All these might contribute to the development of M.aeruginosa dominance in spring in a general trend of the global warming.