Abstract: Excessive concentrations of the sodium ion in soil is a major constraint to plant growth and development. The plasma membrane Na⁺/H⁺ antiporter salt overly sensitive SOS1 is responsible for Na⁺ effluxes from cells, and it plays a crucial role in plant salinity tolerance. Nitraria tangutorum, a shrub belonging to the Nitratia genus in Zygophyllaceae, is a native and typical halophyte mainly growing in deserts or salinity deserts in the northwest of China. It is an excellent species noted for its superior tolerance ability to diverse abiotic stresses. A full length cDNA of NtSOS1 (GenBank accession number KC292267) was isolated from this species by means of degenerate PCR and RACE. NtSOS1 cDNA was 4 008 bp long and comprised a 3 492 bp open reading frame that was predicted to encode a 127.59 kDa protein with 11 hypothetical transmembrane domains within its N terminal portion, and a long hydrophilic cytoplasmic tail with some regulatory domains including cyclic nucleotide binding domain, auto-inhibitory motifs and phosphorylation sites in its C-terminal portion. The amino acid sequences of NtSOS1 show 71.77%, 68.94% and 62.65% identity to homologues from Vitis vinifera, Zygophyllum xanthoxylum and Arabidopsis thaliana, respectively. Phylogenetic analysis showed that NtSOS1 appeared to be a plasma membrane Na⁺/H⁺ antiporter and clustered distantly with vacuolar Na⁺/H⁺ antiporters. The level of NtSOS1 mRNA was clearly up-regulated in the presence of NaCl, PEG, cold and heat stress. Furthermore, NtSOS1 transcript abundance was positively associated with NaCl concentration till 300 mmol/L, while it was reduced under 400 mmol/L NaCl treatment. These results suggest that increased expression of NtSOS1 may be involved in the adaptability of N. tangutorum to the hostile environment. Our work offers a solid foundation for genetic improvement of the crops and herbages with NtSOS1 gene and in-depth study of the molecular mechanisms of stress tolerance of N. tangutorum.