Abstract: This paprer presented a new rooting method--rooting by air-culture,which proceeded rooting of test-tube plantlets of Populus Tomentosa Carr,with saturated humidity air instead of medium.It may simplify the traditional rooting procedure of plant tissue culture.It needn't exactitude sterilization and can be performed out of test-tube.This kind of rooted plantlets has high adaptability to outside environments.So a high survival rate can be gained when it was transplanted.Aplication this method to industrialized micropopagation can acheive a higher propagation index and production efficency,and reduce the cost of test-tube plantlets by 35%or more.Sucrose solution and CO₂ enrichment have a obviously promoting effect on the rooting of microcuttings.