Abstract: Adsorption is an efficiency method to decrease the pollution of 90Sr and 60Co. The adsorption behavior of cobalt and strontium on Fe3O4 magnetic nanoparticles was studied in this paper. The adsorbent applied here was prepared by co-precipitation, and can form waterbased ferrofluids. Its saturation magnetization is 350 kA/m. The experiments show that the Q_max of cobalt and strontium are 1.794 mmol/g and 0.962 mmol/g at pH=7 and pH=8, respectively. The adsorption process follows a pseudosecond kinetics and the Langmuir isotherm, which indicates the adsorption is a monolayer adsorption. 