Abstract: The triethylene-tetramine modified chitosan magnetic sorbent (TETA-MCS) was prepared by the in-situ formation of magnetic chitosan resins in W/O reverse-phase emulsion system followed by the modification of triethylene-tetramine. TETA-MCS was very effective for Th(Ⅳ) adsorption due to its high amine group content and easy magnetic separation. FTIR results indicate that the amine and hydroxyl groups are responsible for the formation of O,N-Th(Ⅳ) complexes. The adsorption process is spontaneous and endothermic, and kinetically follows the pseudo-second-order equation. The adsorption isotherms are correlated with the Langmuir, Freundlich and Tempkin models to show good fits with the Langmuir model, and the maximum adsorption capacity for Th(Ⅳ) is 133.3 mg/g at 25 ℃. The TETA-MCS can be regenerated using 0.2 mol/L HNO₃-0.1 mol/L EDTA and exhibits good reusability.