Disclosed is a serum-free freezing medium used in adipose-derived stem cells and a method for establishing an adipose-derived stem cell library. The serum-free freezing medium comprises a serum-free culture medium, dimethyl sulfoxide and a serum substitution component KSR the defects of unstable freezing quality of the adipose-derived stem cells and influence of harmful factors in serum on the adipose-derived stem cells are solved, and the adipose-derived stem cells stored have the advantages of high survival percentage, well adherence growth and strong differentiation capacity.