Based on the sequence of an expressed sequence tag, the full-length cDNA of 1,008 nucleotides was cloned from Ammopiptanthus mongolicus by rapid amplification of cDNA ends. It was designated as AmDHN, encoding a protein of 183 amino acids. The calculated molecular weight of the AmDHN protein is 18.4 k Da, and theoretical isoelectric point is 5.78. The AmDHN localized in nucleus. Under normal growth conditions, differential expression of AmDHN exhibited that the expression was the highest in seeds and the lowest in flowers. AmDHN could be induced by NaCl, PEG6000, ABA and drought treatments. Salt and drought resistances of transgenic plants with overexpression of AmDHN are improved. Taken together, these results demonstrated that AmDHN could regulate the expression of abiotic-responsive genes and plays important roles in modulating the tolerance of plants to abiotic stresses.