Ephemeral plant Lepidium apetalum Willd. seedlings grow well at low temperatures in early spring in the north of Xinjiang, China, and have a perfect tolerance to low temperature stress. LaNHR2B (cold upregulated expression gene in L. apetalum), a gene found in L. apetalum, was previously reported as being upregulated in seedlings by cold stress. In this study, we obtained the fulllength cDNA sequence of LaNHR2B using homologybased cloning. We predicted and analyzed the nature and conformation of its encoding protein with bioinformatics software, the relationship between its expression and the growth stages of seedlings. We also studied its expression in response to cold induction and exogenous ABA treatment with quantitative RTPCR, and further explored the effects of LaNHR2B overexpression in Arabidopsis thaliana on cold tolerance. Results showed that: （1） the fulllength of LaNHR2B gene is 1 035 bp, encoding a protein consisting of 344 amino acid with a molecular weight of 85 791.16 kD, a theoretical PI of 5.06 and a formula of C₃₁₂₉H₅₂₂₅N₁₀₃₅O₁₃₀₇S₂₃₅. The protein contains alanine, threonine, glycine and cysteine, which has three transmembrane structures with unknown functions and strongly conserved in cruciferous plants. （2） Expression of LaNHR2B was upregulated by cold induction at 4 ℃, but this increase gradually decreased with the growth and development of seedlings, consistent with the decreasing trend of cold tolerance with growth. （3） Exogenous ABA induced LaNHR2B expression, and overexpression of LaNHR2B in A. thaliana enhanced cold tolerance. With these results we have proved that LaNHR2B expression has a close relationship with the cold tolerance of L. apetalum seedlings. Moreover, LaNHR2B may be a functional gene enhancing cold resistance after cold acclimatization, providing a certain theoretical basis and reference for further developing coldresistant breeding of crops with this gene.