Abstract: The effects of different nutrient solution depth on the growth of lettuce were studied by hydroponics with depths of 5cm, 10cm, 15cm. The results are as follows. The changes of pH and EC were both within the normal ranges. The nutrient solution of 10cm depth can satisfy O2 needed by plant per day so long as DO reached saturated DO. The fresh weight and dry weight of lettuce cultivated in 10cm nutrient solution were 124.26g/plant and 10.89g/plant, which increased 21.1% and 28.6% respectively compared with lettuce cultivated in nutrient solution of 5cm depth and the difference was extremely significant