Abstract: Using ripe middle leaves of flue-cured tobacco cv.Honghuadajinyuan as experimental material, the contents of nonvolatile organic acids, lignin, soluble sugar and nicotine in primary veins, primary lateral veins and secondary lateral veins of tobacco leaves were compared.The results showed that veins accounted for more than 60% of the dry weight of whole leaf;the contents of nonvolatile fatty acid, lignin, soluble sugar and nicotine in various leaf veins differed significantly, the veins in order of the contents of saturated fatty acids, unsaturated fatty acids, high fatty acid and nicotine were secondary lateral vein> primary lateral vein> primary vein, while the contents of dicarboxylic fatty acid and lignin were on the contrary;as for soluble sugar content, the order was primary vein> secondary lateral vein> primary lateral vein.