Abstract: The influence of the red-to-blue (R/B) ratio of LED (Light Emitting Diode) light intensity on the physiology and quality of lettuce (Lactuca sativa L.) was studied,to provide the scientific foundation for the application of the artificial light source in the lettuce production. The artificial light source was composed by the red light LED whose wavelength was 660nm and the blue light LED whose wavelength was 450nm in this experiment. Three treatments were designed with LED1 (R/B=10),LED2 (R/B=8) and LED3(R/B=6),compared to treatment of fluorescent lamp(CK). The lettuce was planted by the hydroponic cultivation under different treatments in 30 days. The result showed that the combination of red light and blue light could improve the utilization of light energy and promote photosynthesis. The vitamin C contents would enhance and nitrate contents would reduce effectively though adjusting of R/B ratio. Moreover,in the treatment LED2,the net photosynthetic rate and vitamin C contents were the highest and the nitrate contents were the lowest. The quality and growth of lettuce in the treatment LED2 were better than in other treatments.

Key words: LED, LED, Lettuce, R/B ratio of light intensity