Orn-δ-aminotransferase is the key enzyme for Pro synthesis from Orn, so that it plays an important role in adaptation to environmental stress in plants. A 425-bp segment was cloned from tobacco（Nicotiana tabacum,zhongyan 14）using degenerate primer designed from the known conserved regions of Orn-δ-aminotransferase gene. Special primers derived from the 425-bp segment were used to amplify the 5’ and 3’ ends of the cDNA by RACE. Comparison and analysis of the sequence was performed with BLAST which proved that it was the first time to get the clone of Orn-δ-aminotransferase gene from tobacco. The full-length cDNA was termed Ntδ-OAT (GenBank accession GU144571) which was 1,781 bp in length and encoded a protein of 477 amino acids. According to phylogenetic tree, the evolution of Ntδ-OAT corresponds with traditional biological classification. Its functional domain has a high conservative property in the process of biological evolution. By the analysis of real-time PCR, It was determined that Ntδ-OAT could express under many inducements such as drought, high salt, low temperature, ABA and so on, from which we might conclude that Ntδ-OAT plays a role in the resistance to osmoticstress.