Ammonium molybdophosphate (AMP) was incorporated in the porous alumina matrix (JA) by successive impregnation with H3Mo12O40P and NH4NO3. The loading percentage of AMP crystals on JA increased with the repetition times of impregnation. The distribution coefficients of Csf on AMP-loaded granular composite (JAAMP) was above 10(4) cm(3)/g in the presence of 1 mol/dm(3) H+, while those of other nuclides were less than 10, indicating high selectivity of JAAMP to Cs＇. The separation factor of Cs-137 to other nuclides (Sr-85, Co-60, Eu-152, Am-241, Na-22) (alpha(Cs/Sr;Co:Eu;) (Am;Na) = K-d,K-Cs/K-d,K-Sr;Co;Eu;Am;Na) was estimated to be above 10(3). The breakthrough curve for Cs+ through the column packed with JAAMP exhibited a symmetrical S-shaped profile, and this exchanger proved to be effective for the selective isolation of radiocesium from a simulated high-level liquid waste.