Flue-cured tobacco cultivar Yunyan87 was used as material and 2 factors and 3 levels orthognoal test was designed to clarify the effect of auxin(0 mg/L, 10 mg/L, 20 mg/L) and brassinolide(0 mg/L, 10 mg/L, 20 mg/L) on leaf area, plastid pigment, conventional chemical composition, the main neutral fragrance substances of flue-cured tobacco. The results showed that application of auxin after topping increased tobacco leaf area, and decreased nitrogen content obviously and application of brassinolide after topping increased tobacco leaf area. Tobacco leaf chlorophyll content and plastid pigment total contents were increased under spraying with 20 mg/L auxin. Tobacco leaf area significantly increased and pigments index were obviously increased under spraying with 10 mg/L auxin combined with 10 mg/L or 20 mg/L brassinolide; and the total nitrogen content, chlorine content decreased significantly in the flue-cured tobacco with increased main neutral fragrance substances. After topping, spraying with 10 mg/L auxin and 10 mg/L brassinolide promoted the tobacco leaf opening, improved the content of the plastid pigment and its degradation products, improved the potassium content and potassium chlorine ratio of tobacco leaves and reduced chlorine and niacin content.