Abstract: An in situ method for rapidly determining the lignin content in tobacco was developed with mid-infrared (MIR) spectrometry, and the lignin contents in ground tobacco stem and leaf were separately determined by this method. The calibration curve of the lignin content in tobacco was obtained on the basis of absorption peak area of lignin at 1508 cm^-1 with determination coefficient of 0.9914. The results showed that the lignin contents in the ground stem and leaf of B1F burley tobacco in "Shuangxi" brand were 2.45% and 1.21% with the relative standard deviations of 3.88% and 4.17%, respectively. The average recoveries of this method ranged from 96.96% to 106.01%. With good reproducibility, this method is simple in operation and rapid for determining the lignin content in tobacco.