Through RT-PCR (reverse transcription polymerase chain reaction) and RACE (rapid amplification of cDNA ends),a 1 683 bp fragment containing entire Na⁺/H⁺ antiporter coding region of 560 amino acids (aa) has been obtained from extreme xerophyte and salt-tolerant plant Haloxylon ammodendron.The amino acid sequence contains a high conservative sequence-binding domain of amiloride (LFFIYLLPPI).The nucleotide sequence of HaNHX cDNA shared 70%~80% identity with that in the same families,and 60% identity with those of other families.This analysis suggested that the HaNHX genes are evolutionarily diversified although they all have a binding domain of amiloride and a high specificity on Na⁺ which is of great importance in salt tolerance.