The responsive to dehydration protein 22s (RD22s) constitute a subfamily of the plantspecific BURP domaincontaining protein family, which are closely related to stress tolerance of plants. In this study, the fulllength cDNA for a RD22 gene (AmRD22) was cloned from Ammopiptanthus mongolicus, a plant endemic to desert areas in Northwest China and with strong tolerance to abiotic stresses. Moreover, its coding protein, expression pattern and biological function in stress tolerance were analyzed. The results showed that: (1) the AmRD22 protein (360 aa) contains all four domains common to the RD22 subfamily and it most probably locates in cell wall. Among the reported RD22 proteins with known biological function, AmRD22 has the closest phylogenetic relationship with soybean GmRD22. (2) In laboratorycultured A. mongolicus seedlings, the expression of AmRD22 was induced by dehydration, high salinity, cold and exogenous ABA, and the induction was relatively high under the dehydration and cold stresses. In young leaves of A. mongolicus adult plants growing in the wild, the expression levels of AmRD22 were markedly high from the midautumn to the midwinter compared to those in other seasons. (3) Transgenic Arabidopsis with AmRD22 gene showed significantly enhanced salt tolerance and lowered Na⁺ content. The transgenics also showed improved drought tolerance and reduced ABA sensitivity at early seed germination stage but had no obvious change in chilling and freezing tolerances.