Microcystis aeruginosa is one of the most common species in the algae-bloom events of domestic lakes. Illumination incubator was used to cultivate M. aeruginosa under conditions of different phosphorus concentrations in the laboratory. Spectroscopic data of culture solutions were collected by GER1500 spectrometer under the sunlight. The study focused on the growth rhythm of M. aeruginosa and the characteristics of spectral variation in the culture solutions. The results showed that low phosphorus concentration (≤10 μg·L-1) is a restricting factor for the growth and reproduction of M. aeruginosa. Moreover, the reflections of spectrum from culture solutions of M. aeruginosa showed significant changes along with cultivation period, such as at the wavelengths of 550, 610, 660, 700～710 and 760 nm.