Abstract: Lettuces of green and purple leaves were planted with hydroponics under LED light of different blue light ratio and fluorescent light，and the growth of the lettuces were studied.The two leaf-color lettuce under RB 2∶1（RBⅠ）got the highest photosynthetic pigment content.Photosynthetic pigment contents decreased as the ratio of blue light got lower，so it was lowest under RB 1∶2（RB Ⅲ）and flourescent light（F）.And sensitivity degree of green lettuce photosynthetic pigment to light quality was higher than that of purple lettuce.The green lettuce got highest shoot fresh weight，root fresh weight and shoot dry weight under RB 1∶1（RB Ⅱ）.Shoot fresh weight of purple lettuce was the highest under white light（W）.Root fresh weight and root dry weight of purple lettuce were the largest under RB 2∶1（RBⅠ）.However，shoot dry weight was not sensitive to the ratio of red and blue light.RB 1∶1（RB Ⅱ）and white light（W）were the most suitable to the growth of green lettuce and purple lettuce respectively.