Abstract: In order to explore the feasibility of phenol oxidase treatment on improving the quality of burley tobacco leaves, phenol oxidase was applied to the surface of un-aged burley tobacco produced in Enshi City of Hubei Province, and its effects on the chemical composition and quality of burley tobacco leaves at different catalytic temperatures, dosages and catalytic time were studied. The results showed that phenol oxidase could promote the change of various chemical components in burley tobacco, including reducing the contents of tobacco-specific nitrosamines (TSNAs) and phenolic substances, and promoting the accumulation of esters. In addition, the effect of phenol oxidase on total sugars and reducing sugars, total phytobases and ketones in tobacco leaves was significantly affected by the catalytic conditions. After 24 hours of treatment using 20% phenol oxidase at 50 ℃, the contents of TSNAs, phenolic aroma compounds, and ketone aroma compounds in tobacco leaves decreased by 20.04%, 27.08% and 21.29%, respectively. The contents of reducing sugar, total sugar and ester aroma compounds increased by 44.92%, 29.02% and 11.27%, respectively. The scores of multiple indicators such as aroma quality, aroma amount, offensive odor, concentration, and irritation of burley tobacco increased by more than 1 point, indicating that the quality of tobacco leaves was improved. The results show that the application of phenol oxidase to un-aged burley tobacco leaves can quickly coordinate their intrinsic chemical components and improve their quality.