Abstract: Alginate-potassium nickel hexacyanaferrate (ALG-KNiFC) composite adsorbent was synthesized by self-made device, and its structure was analyzed by utilizing the techniques of SEM, FT-IR and EDS. The effects of contact time, pH, initial concentration of Cs⁺, co-existing ions on Cs⁺ adsorption were investigated via batch experiments. Equilibrium is achieved after about 3 h, its saturated adsorption capacity is 190 mg/g, and its adsorption capacity decreases in the strong acidic or alkalic solution. NH⁺₄ which reduced 20% of removal rate of Cs⁺ by adsorbent shows the most significant inhibitory effects among all the co-existing metal ions, with other ions within 10%. The analysis about adsorption mechanism according to thermodynamic model and other models indicates that Cs⁺ adsorption by ALG-KNiFC is monolayer and chemical, and intraparticle diffusion and liquid film diffusion control their rates of adsorption simultaneously.