Abstract: In order to explore the effects of nitrogen and potassium on tar content and chemical properties in middle leaves of flue-cured tobacco in Jilin province, an interaction experiment with two factors and three levels of nitrogen and potassium was arranged in Yanbian city of Jilin province. The chemical properties and tar delivery in middle leaves of flue-cured tobacco were determined. The results showed that the best treatment to reduce tar delivery was N 45 kg/hm² with K₂O 180 kg/hm². Adding K₂O reduced tar delivery in the range of 90~180 kg/hm². But there was a rising trend of tar delivery when the application of potassium overdosed. Reducing the amount of nitrogen also played a role in reducing the tar delivery when the amount of potassium fixed at 90 kg/hm² and 180 kg/hm². Nicotine and TN was significantly positively correlated with tar delivery. Tar and cellulose showed a significant negative correlation. Tar and sugar was extremely significant negative correlation. Nicotine and TN not only have a greater direct role, but also assisted other chemical properties to have a greater indirect effect on tar delivery. Comprehensive studies showed that through appropriate nitrogen and potassium as well as control some chemical properties of the tobacco can achieve the purpose of reducing the tar delivery while reducing risk.