Abstract: The artificial light plays an important role in crop growth, and LED as a new light source has broad prospects in the development of supplementary lighting system. According to the deficiency of fixed light intensity and light spectrums, this paper presented a self-adaptive and precise supplementary lighting system with comprehensive consideration of crop characteristics, effective photosynthesis light intensity and environment temperature. The system monitored the environment temperature and light intensity of specific light spectrums, and calculated the amount of supplementary light accurately. Based on two PWM signals, both red and blue light intensity were adjusted to meet different demands of quantitative supplementation of light in different stages and conditions. Experiments were made in actual production. The results showed that the system was stable, reliable and accurate, and could avoid the lacking or excess supplementation of light in different stages of crops.