A method to separate Kanamycin A and B from their fermentation broth is proposed in this paper. In order to seek Kanamycin B-sensitive resin, the equilibrium constants of Kanamycin B were estimated by potentiometric titration, and then the resins for test were evaluted by static and dynamicabsorption. The results indicated that the 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%.