The automatic classification of tobacco leaves has been an important intelligent research field.By studying on the components of tobacco leaves and analyzing the spectrum of tobacco leaves,the infrared spectra of tobacco leaves can be used as stamp of the tobacco grading.This is verified by the neural network model.The best intervals of the infrared spectra and the necessary preprocessing algorithm are studied and decided.400 infrared spectra of tobacco leaves are adopted to group or grade leaves by neural network model.Almost half leaves are used as training samples and others as test samples.The mean rates of correct fit classification are 100% and 91% for training and test samples respectively.The grouping and grading results of neural network model based on infrared spectra show that the infrared spectra can be applied to grade tobacco leaves automatically.This indicates it is a new method for the automatic grading tobacco leaves.