Light is one of the precipitating factors of red tide, and the intensity of light plays a key role on the growth of red tide advantage algae. Monochromatic LEDs are used as the light source to cultivate dinoflagellate Prorocentrum lima and diatom Skeletonema costatum. When temperature and light cycle are fixed, to investigate the effect of different light intensities of green, red and blue light on the growth rates and spectrum absorption coefficient of algae is investigated. The results show that the saturated light intensity of blue light of Prorocentrum lima and Skeletonema costatum are the lowest, and the saturated light intensities of red light of Prorocentrum lima, and green light of Skeletonema costatum are the highest, respectively. Within saturated light intensity and the same light intensity, the growth rates of Prorocentrun lima and Speletonema constatum are the largest in blue light, but lowest in red and green light, separately. Besides, it is concluded that the growth rates of two algae are positive to the spectrum absorption coefficient, while saturated light intensity is negative to the spectrum absorption coefficient under different monochromatic lights.