Abstract: After drought stress the changes of the carbon and nitrogen metabolism and osmotic adjustment on tobacco with 35S: BnDREB1-5 transformation were analyzed. The results indicated that after physical drought-stress the carbon metabolisms of transgenic tobacco, which included the amylase activity, the invertase activity and the soluble sugar content, increased significantly, and the amylase activity and the soluble sugar content of wild-type increased slightly, but the invertase activity of wild-type decreased. The nitrogen metabolisms of transgenic tobacco, which included the nitrate reductase activity and the soluble protein content, decreased slightly, while those of wild-type tobacco decreased significantly. The BADH activity of transgenic tobacco leaves was detectable and increased after drought stress, but that of wild-type was not detectable. After drought stress, the proline content of transgenic tobacco leaves was 1.08 times as large as that of wild-type. After drought stress the carbon and nitrogen metabolism and defense activity on tobacco with 35S: BnDREB1-5 transformation were obviously better than wild-type.