Salix matsudana is a willow that is tolerant of salinity, but the mechanisms behind this are not fully understood.Here, we isolated a full-length 1080 bp cDNA for a salt stress-responsive cysteine protease from S.matsudana, designated as SmCP.The deduced 359-amino-acid SmCP protein, showing high identity to cysteine proteases of other plant species, was predicted to contain inhibitor-I29 and peptidase-C1A domains with three active catalytic sites found in eukaryotic cysteine proteases.