Abstract: The effects of different floating plate types on lettuce（Lactuca sativa L.） cultivated by floating hydroponics technique were studied. The results showed that the effects of the double-layer floating plate with the upper and lower thickness of 2 cm of lettuce was the best. The plant shape was large. It’s plant height was 26.72 cm, plant width was 32.15 cm,stem diameter was 10.90 mm, leaf number was 9.81,leaf length was 23.56 cm,leaf width was 14.63 cm,leaf area was 229.78 cm², and root volume was 9.54 cm³. The biomass was high. It’s fresh mass of crown was 47.51 g,fresh mass of root was 9.48 g, total fresh mass was 56.99 g, dry mass of crown was 3.037 0 g, root dry mass was 0.935 3 g,total dry mass was 3.972 3 g. The nutritional quality was similar to that of conventional lamp core. Therefore, the double-deck floating plate that comprised two pieces polystyrene foam plastics plates, one piece’s thickness was 2 cm and the fixed holes diameter was 2 cm,the other piece’s thickness was 2 cm and the diameter of planting hole was 5 cm, can be used for hydroponics of leaf lettuce.

Key words: soilless culture, hydroponics, floating plate, lettuce（Lactuca sativa L.）