Abstract: The floating system of flue-cured seedlings is an adoption to have no the soil facilities the roasting of cultivation principle the smoke to teach the new technique of seedling. This experiments to pass two years many times and again and again on trial, and study the different light to shine on the strength to influence roast smoke afloat taught seedling grew strengthen seedling the function.The strength of light was different at differ time. At early time, from germination to 2 leaves of seedling, the best light strength was 4000-10000 LAX and covered 1 layer of black plastic. The 75% of light was shed. At middle time, 2 leaves of seedling, the best light strength was 10000-18000 LAX and uncovered 1 layer of black plastic. And the later time, 5 leaves of seedling, the best light strength was 12000-30000LAX and uncovered all the plastics. Guarantee the light to shine on the strength.