A set of 7 ku proteins (named cold shock proteins) is strongly induced in response to a rapid decrease in growth temperature when bacteria adapt to temperatures below their growth temperature. They are rich in aromatic and basic amino acids, suggested to function as molecular chaperones and make cell enhance ability to survive freezing after a cold shock treatment. The similarity and difference of cold shock proteins were described in structure, regulation of expression and function etc. In addtion, the value of them for human kind is in mention.