Calmodulins (CaMs) are highly conserved Ca2+ sensor proteins and play important regulatory role in Ca2+ signal transduction. In the present study, we analyzed the expression patterns of AmCaM1 in Ammopiptanthus mongolicus, a plant with very strong resistance to adverse environments, under abiotic stresses. We then cloned this gene and constructed its plant expression vector. We also transformed Arabidopsis thaliana with AmCaM1and performed a preliminary analysis of its function. The results showed that the transcription levels of AmCaM1 were rapidly up-regulated by cold, drought and salt stresses; the complete coding region cDNA of AmCaM1 contains 450 base pairs and encodes a protein consisting of 149 amino acid residues. Four conserved EF-hand motifs exist in the primary structure of AmCaM1 protein. The transgenic Arabidopsis lines of AmCaM1 showed enhanced tolerance to water stress but had no obvious change in salt and cold tolerances during their seed germination.