Abstract: Effect of application of varied amounts of phosphorus(P)on the growth and physiological characteristics of the seedlings of flue-cured tobacco K326 was studied.It was found that the length,tip,surface area,volume and rigor of the roots increased with increasing P at low levels.The activities of POD,PPO,PAL and stress resistance also increased significantly(P<0.01).In addition,the P fertilizations enhanced the chlorophyll content and net photosynthetic rate,as well as the assimilating capability of the seedlings.The amount of P appropriate for the seedling growth on a floating bed was determined to be 15-18 mg·plant-1.At this rate,the development of tobacco seedlings was shown healthy with strong roots,highly resistant to stresses and diseases,and desirable photosynthetic functions.