Nano-TiO2 was employed for the separation and preconcentration of thallium. It was found that the adsorption ratio of thallium ions was more than 98% at pH 4.5 and the desorption ratio reached 99% under microwave irradiation for 3 min at 350 W. The adsorption equilibrium was well described by the Langmuir isotherm model with a maximum adsorption capacity of 4.09 mg/g[(20±0.1) C]. The nano-TiO2 was successfully applied to the determination of element thallium in the certified reference material polymetallic nodule and water samples.