In order to solve the problem of poor sensory quality caused by the high content of starch and protein in tobacco leaves, a method for degrading starch and protein without affecting the workability of tobacco leaves was investigated. In this study, formic acid was used as catalyst to spray proper amount on tobacco leaves. The hydrolysis of starch and protein in tobacco leaves catalyzed by formic acid, which played an effective role in regulating and reducing the starch and protein content. When the concentration of formic acid ranged from 5% to 10% at 50 ℃, with the sprinkling rate of 0.2 mL/g formic acid solution to the tobacco leaves, the appearance quality and microstructure of tobacco leaves were unchanged significantly, and the workability was still fine. The results of FTIR spectrum presented that the peak intensity of characteristic functional groups of starch and protein in tobacco leaves decreased obviously after formic acid treatment. The starch and protein of tobacco leaves could be effectively degraded by formic acid, and the degradation rate was positively correlated with the concentration of formic acid. The hydrolysate of protein is polypeptide and amino acid, and the hydrolysate of starch is polysaccharide and monosaccharide, which can transform into aroma components by Maillard reaction. The results of sensory evaluation showed that the tobacco treated by appropriate concentration of formic acid had less taste impurity, more aroma and better quality.