Abstract: Cs⁺ in liquid radioactive waste of nuclear power plant has the characteristics of long half-life, strong radioactivity and high ionization in water, which seriously endangers ecological environment and human health. Therefore, the effective removal of Cs⁺ is of great significance for the safe operation of nuclear power plant and the protection of ecological environment. At present, Cs⁺ is mainly removed by ion exchange method in nuclear power plants, but the nuclear grade resin used has the problem of poor selectivity for Cs⁺. Ferrocyanide(KMCF) has excellent adsorption capacity and selectivity for Cs⁺, and is a promising adsorption material for Cs⁺ removal. However, due to its fine particles, poor mechanical strength and high flow resistance, it is not suitable for column operation. In this paper, a novel composite adsorption material was prepared by using potassium nickel ferrocyanide(KNiCF) as the functional material and potassium montmorillonite(K-MMT) as the carrier. The materials microstructure and composition were characterized by Fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM). The results indicate that KNiCF/K-MMT adsorption materials have pore structure, with successfully loaded of KNiCF. Futhermore, thermogravimetric differential thermal analysis(TGA) supported the high thermal stability of KNiCF/K-MMT. The adsorption performance of KNiCF/K-MMT on Cs⁺ was determined by static and dynamic adsorption experiments. On the hand, the static adsorption experiment investigated the effect of initial concentration of Cs⁺, adsorption time, temperature, pH and interference ions on the adsorption process. The result of static adsorption experiment indicates that the adsorption of Cs⁺ by KNiCF/K-MMT reachs equilibrium after 8 h. The adsorption isothermal process and adsorption kinetics process are in line with the Sips adsorption isothermal model and pseudo-second-order kinetic model, respectively. The result indicates that the maximum adsorption capacity of Cs⁺ is 138.5 mg/g and the adsorption rate constant k₂ is 3.23×10⁻⁴ g/(mg•min). It demonstrates that KNiCF/K-MMT shows magnificent adsorption capacity and kinetics of Cs⁺. The adsorption capacity of KNiCF/K-MMT for Cs⁺ is positively correlated with reaction temperature. The absorption process of Cs⁺ by KNiCF/K-MMT is spontaneous endothermic reaction with adsorption enthalpy equal to 43.03 kJ/mol. Under the condition of pH=5-8, the adsorption capacity of KNiCF/K-MMT for Cs⁺ increases first and then decreases with the increase of pH value. KNiCF/K-MMT shows the max adsorption capacity for Cs⁺ under neutral conditions. In addition, KNiCF/K-MMT shows magnificent selectivity for Cs⁺. Except for Sr²⁺, the selectivity coefficients of KNiCF/K-MMT for other interfering ions(Na⁺, Mg²⁺, Fe³⁺, Co²⁺, Cr³⁺, and Mn²⁺) α_Cs/M are more than 50. On the other hand, the dynamic adsorption experiments investigated the effect of feed flow rate, bed height, and Cs⁺ initial concentration. The experimental results are fitted by different dynamic adsorption model, namely Thomas and Yoon-Nelson dynamic adsorption model. Both models have a preferable fitting degree(r²>0.95) for the dynamic adsorption process. The result of fitting demonstrates that the adsorption process is a single molecular layer adsorption on a uniform surface, and neither internal diffusion nor external diffusion is the control step of the adsorption process. Based on the advantages of pore structure, abundant adsorption sites and low mass transfer resistance in adsorption column. KNiCF/K-MMT has well adsorption and selection performance for Cs⁺, which has application potential in the treatment of wastewater containing Cs⁺.