The cigar variety CX81 was used to study the material basis of nitrogen application rate affecting the sensory quality of cigar tobacco and analyze the flavor characteristics of cigar tobacco leaves in Hunan Province. 4 treatments of nitrogen application rate including N0 （0 kg/hm²， CK）， N1 （180 kg/hm²）， N2 （210 kg/hm²） and N3 （240 kg/hm²） were set up to determine the sensory quality and main chemical components of fermented tobacco leaves. The orthogonal partial least squares discriminant analysis （OPLS-DA） was used to screen key differential indexes and analyze their relationship with sensory quality. The results showed that the increase in nitrogen application rate enhanced the intensity of smoke， the rich and mellow degree， pollen aroma， and glutinous rice aroma of cigar tobacco. The content of total nitrogen， nicotine and browning reaction products in cigar tobacco leaves increased significantly with the increase of nitrogen application rate. The total amount of phenylalanine degradation products， carotenoid degradation products， the neophytadiene and neutral aroma substances increased first and then decreased， while the content of total sugar， reducing sugar， and cembranoid degradation products gradually decreased. There was no unique chemical component in cigar tobacco leaves under different nitrogen application rate， and the proportion of components with increased content of chemical components gradually increased with the increase of nitrogen application rate. 21 key differential components were screened， of which 7 were significantly positively correlated with sensory quality and 2 were significantly negatively correlated. It is indicated that increasing the application of nitrogen fertilizer can increase the total amount of neutral aroma substances （except for neophytadiene）， thereby enhancing the sweetness and woody aroma of cigar tobacco. The intensity of smoke， the rich and mellow degree in smoke were further enhanced， and the pollen aroma and glutinous rice aroma were enriched by increasing the content of total nitrogen， nicotine， benzaldehyde， furfural， 3，4-dimethyl-2，5-furanedione， and browning reaction products， and reducing the mass fraction of reducing sugars.