A　series　multicolumn　of　cation-exchange　was　employed　in　this　investigation　to　separate　Kanamycin　A　and　B　from　their　fermentation　broth.　In　order　to　choose　Kanamycin　B-sensitive　resin,　the　equilibrium　constants　of　Kanamycin　B　were　first　estimated　by　potentiometric　titration,　and　then　the　resins　for　test　were　evaluated　by　static　and　dynamic　absorption.　The　results　indicated　that　weak　acid　resin　D4　with　larger　mesh　has　higher　adsorption　rate　of　Kanamycin　B　and　lower　adsorption　amount　of　impurity.　Using　D4　as　first　column　and　732(#)　as　late　binding　columns,　the　purity　of　Kanamycin　A　is　higher　than　99.0%.