Abstract: In order to understand the changes of flue-cured tobacco leaf tissue structure and mature leaf chlorophyll content under different forms of nitrogen situation with pot experiment, the changes of leaf’s tissue and the content of chlorophyll of flue-cured was studied during the period of maturation under the different nitrogen forms. The result indicated that: The flue-cured tobacco that under different nitrogen form treating, the leaf thickness, the thickness of upper epidermis, the mesophyll organization increased with the increase of maturity degree, and each processing is various different in its range of fall in mature period. In suitable ripe stage，the leaf thickness of NH₄⁺-N 50%＋NO₃--N 50%（T1）is moderate and advantage to bake and improve the quality of tobacco. In different mature period, the leaf chlorophyll content in P<0.05 under three different nitrogen forms was significant different with each other. The content of chlorophyll all was decreased with the increase of maturity degree under three nitrogen forms. The range of fall fell bigger at the time from decides as long ripe to as at the beginning of in the ripe and from the beginning of in the ripe to the suitable ripe. Such primary results were raised to satisfy the production of high-quality tobacco leaves.