The core-shell magnetic nano-composite Mn3O4@SiO2 was prepared by oxidation and hydrolysis of tetraethyl orthosilicate (TEOS), and the adsorption performance of Mn3O4@SiO2 nanocomposite was explored for the adsorption of Mo (VI) ions from aqueous solutions. The core-shell magnetic nano-composite Mn3O4@SiO2 was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy and magnetmeter (VSM) et al various methods. The effects of solution initial pH, Mo (VI) ion initial concentration and temperature on the amount of Mo (VI) adsorbed were studied. The results showed that the maximum adsorption capacity of the Mn3O4@SiO2 composite for Mo (VI) is 145.35 mg/g at 298 K. The adsorption process of Mn3O4@SiO2 composite is agreed well with Langmuir adsorption isotherm models and pseudo second-order kinetics. The thermodynamic analysis revealed that the adsorption process of Mn3O4@SiO2 composite for Mo (VI) was spontaneous and endothermic.