The Arabidopsis thaliana AtNHX2 gene is one member of the Arabidopsis NHX Na⁺/H⁺ antiporter gene family and play an important role in salt tolerance. A sequence-analyzed 2.8 kb DNA fragment on upstream of ATG start codon of AtNHX2 gene was cloned into pCAMBIA1301-1. The promoter activity was detected by transient expression in onion epidermis. The reconstructed vector pCAMBIA1301-1/ AtNHX2 promoter was transformed into Arabidopsis thaliana by Floral Dip method. AtNHX2 promoter-GUS analysis in transgenic Arabidopsis showed that AtNHX2 was expressed in all tissues. Strong GUS expression was detected in guard cells suggesting the possibility that it is involved in stomatal regulation. AtNHX2 promoter activity was decreased by NaCl and up-regulated by KCl, demonstrating that NaCl and KCl regulation to AtNHX2 expression occurs at the transcriptional level. GUS activity in old leaves was higher than in new leaves, which reveals a role of AtNHX2 in salt tolerance. Strong GUS activity in root hair cells was observed. It suggests that AtNHX2 may play an important role in partitioning of Na⁺ into the enlarged vacuoles of root hair cells.