Potassium cobalt hexacyanoferrate(KCoFC) was prepared to remove cesium ion and its structure was confirmed by X-ray diffraction method. The chemical stability of KCoFC was tested in the range of pHl ~ 4 and it was stable in acidic solution. Ion exchanger behavior for Cs ion using KCoFC were examined by batch method and its selectivity was determined by distribution coefficient. The distribution coefficients of for Cs and Sr ions were 4.5×10^3 mL/g and 45 mL/g, respectively. In the multi-component system, the separation factors of KCoFC for Cs/Sr, Cs/Na, Cs/Sr+Na ion showed the highest values at pH2.