Abstract: To solve the problem of the dissolved oxygen in deep flowing technique(DFT), the authors designed four different installations. And to study the effects of the four different DFT installations on yield, quality of lettuce, the authors performed experiments on Italian very late bolt lettuce. The results show that the installation of circulating floating system(CFS) can supply plant with needed nutrient and oxygen, every index of yield reaches the highest level and the quality indexes reach perfect level; The installation of supported floating system(CFS) cannot ensure a large amount of oxygen dissolve in nutrient solution but because of the roots exposing the atmosphere can absorb the oxygen in the air, the plants develop well. The content of vitamin C is the highest and the Nitrate is the lowest which has extremely remarkable difference from the plants in the other three treatments. Meanwhile, floating system and dynamic solution surface restrain the growth of plants in some aspects. If people want to use these two systems they need to modify some parameters of their structures and circulating system. From the results of this experiment, SFS is the best DFT system in Beijing.