Abstract: In order to enhance the quality and quantity of aroma of the Hunan flue-cured tobacco, increase its industry usability; The effects of different lasting time and humidity conditions during the crucial temperature phase in the flue-cured tobacco curing on the aroma were studied by using the electric-heated temperature and humidity auto-controlled flue-curing barn supplied by Henan Agricultural University; The results indicated, when entering the crucial temperature phase ahead of time and keeping long time, cooperating suitable humidity, which could enable the tobacco yellowing sufficiency, increase its appearance quality. And the starch degradation more completely, the content of total sugar and reduced sugar added, the chemical components also became harmonize；which improved the aroma and inner quality of flue-cured tobacco in some degree, increased its quality and usability.