Novel porous permutite/carbon nanobeads/amidated alginic acid nanocomposites were successfully fabricated via a gamma radiation method. The carbon nanobeads are 40–60 nm in diameter. The cross-linked amidated alginic acid is well dispersed on the surface of carbon nanobeads and permutite. The preparation parameters such as reactant ratio, carbonization conditions and radiation dose were optimized. The influences of contact time, pH and initial concentration of the Cs⁺ solution were investigated. Contact time = 4 h and pH = 9 are ideal conditions for Cs⁺ removal. The Cs⁺ removal efficiency and adsorption capacity can reach 98% and 60.1 mg g⁻¹ respectively. They have good stability and adsorption–desorption properties. The adsorption capacity can maintain more than 85% after 4 adsorption–desorption cycles. The preparation strategy and adsorption mechanism were also discussed. Gamma radiation technology exhibits distinguished advantages to improve the dispersion and stability of organic/inorganic hybrid materials. This method can be easily applied to prepare other similar porous hybrid adsorbents.