Abstract: Microorganisms, ever applied to remediation of heavy metal polluted soils, seems to be a prospective approach in radioactive contamination remediation. In our work, Aspergillus F77 was separated from high-level radioactivity soils and used to remove Cs⁺ from aqueous solutions. Effects of pH values, initial concentration of Cs⁺, concentration of kalium on the biosorption of Cs⁺ by Aspergillus F77, as well as the kinetics and thermodynamics, were investigated through batch progress. The results indicate that acids, including organic acids generated in the metabolism of Aspergillus F77, inhibite the growth of the aspergillus intensively. The effective biosorption of Cs⁺ was found to be in the pH range of 2.0-3.5, probably because of the decrease of competition adsorption of H⁺. When the concentration of Cs⁺ is 500 mg/L, the amount of Cs⁺ sorpted by Aspergillus F77 attains the maximum value of 27.6 mg/L. The present of kalium has no significant effect on the biosorption of Cs⁺ when the concentration of kalium falls in the range of 0-500 mg/L, however, inhibits it evidently when kalium ions exceeds 500 mg/L, which is attributed to the competitive adsorption of the homologous kalium. Kinetics studies show that the biosorption equilibration is achieved within 70 h. Due to its high biosorption ability to remove Cs⁺ from aqueous solutions, Aspergillus F77 can be a potential biosorbent in biological remediation of Cs⁺ contaminated waters.