Abstract: As one of the most notorious long-lived radionuclides with strong radioactivity, Cs⁺ is particularly difficult to sequester due to its alkali-metal-ion chemical properties. Therefore, selective Cs⁺ adsorbents are urgently needed in radioactive wastewater treatment. Stabilized potassium hexacyanoferrates(Ⅱ) have proven effective for selective Cs⁺ removal; however, their practical application is severely constrained because they are typically obtained as nano- or microparticles that are extremely difficult to granulate. When granulated or supported particles are subjected to water flow, fine solids tend to be washed away, significantly increasing the radioactivity of the effluent due to the entrained Cs⁺-laden particulates. To address this issue, composite materials with high selective Cs⁺ uptake were prepared by incorporating stabilized potassium hexacyanoferrates(Ⅱ) into porous spherical activated carbon. The spherical activated carbon support was derived from strong-acid ion-exchange resin beads through calcination and activation. Using a rationally designed procedure, co-precipitation reactions that yield stabilized potassium hexacyanoferrates(Ⅱ) were conducted within the internal pores of the spherical carbon. The resulting composites were characterized by XRD, N₂ adsorption-desorption(BET method), SEM-EDX, and ICP-OES/MS. The results show that the specific surface areas of the samples exceed 700 m²/g, with micropores, mesopores, and macropores all being present. It can be safely concluded that the stabilized potassium hexacyanoferrates(Ⅱ) were successfully embedded in the inner crevices of the porous spherical activated carbon, and the composites exhibited excellent selective Cs⁺ capture ability, with distribution coefficients(K_d) of 344170, 57919, and 42540 mL/g in the presence of 0.1 mol/L Na⁺, K⁺, or H⁺, respectively. Under strong acid interference(1.0 mol/L HNO₃), the sample using copper-stabilized potassium hexacyanoferrate(Ⅱ) as the active ingredient achieved the highest K_d of 14692 mL/g. In the presence of concentrated K⁺(1.0 mol/L), the cobalt-stabilized analogue gave a K_d of 92872 mL/g. The outer shell of the porous spherical carbon is permeable to water and ions but impermeable to the stabilized hexacyanoferrate(Ⅱ) nanoparticles. Hence, the active sites remain fully accessible to Cs⁺ in solution without being washed away, and the treated liquids remained completely colorless. Moreover, the smooth shell endows the composites with good abrasion resistance and crack-proof properties, preventing pulverization or scaling-off during solid-liquid contact. These characteristics make the prepared materials a promising candidate for treating real radioactive wastewater.