Abstract: LED plant growth lights were used as supplemental illumination material in this study. The effect of different duration of supplemental illumination on the growth of melon was investigated by using a single factor of completely randomized block experimental design. The results showed that in the whole growth period of the test， the VC content was the highest in the treatment of supplemental illumination for 1 hour; the plant height and fruit longitudinal growth were greatly promoted with the highest soluble solid content in the treatment of supplemental illumination for 3 hours; after supplemental illumination for 5 hours， the stem diameter was promoted， the plant fresh and dry weight were significantly affected， soluble sugar content and sugar acid ratio were the highest; the yield was the highest in the treatment of supplemental illumination for 7 hours. When the light was added for 7 hours at seedling stage， 5 hours at the vine elongation stage， and 1 hour at fruiting stage， the growth and quality of melon was the best.

Key words: LED plant growth light, melon, quality, yield, sunlight greenhouse