Abstract: To accurately determine the stalk position of tobacco in leaf grading, 12 samples of four orange colors from three stalk positions of cv. K326 were selected from Qujing in Yunnan. Their shape, weight per unit length, color and mechanical property from the midribs of leaves were studied to identify different stalk positions by combining images with experimental data. The results showed that:lower leaves possessed straightly closed midribs, plain surface with low lignification degree and "floating" feel; their midribs were thin, soft, light yellow or yellow in color, and easy to break with the average weight per unit length of 0.066 g/cm. Middle leaves had half covered midribs, oily and wrinkled surface, a higher lignification degree and "real" feel; their midribs was moderate in thickness, deep yellow or light brown in color and harder to break with the average weight per unit length of 0.104 g/cm. Upper leaves possessed straight and completely revealed midribs, folded and wrinkled surface, with the highest lignification degree and "heavy" feel; their midribs were hard, brittle, black or dark brown in color and the hardest to break with the average weight per unit length of 0.151 g/cm.