In this study, the new magnetic nanoparticles modified with chitosan were prepared by reverse suspension cross-linking method to solve the problem of excess molybdenum in mining wastewater. The materials were employed for the adsorption of Mo (VI) from water. By adjusting the pH value of the water sample, the adsorption process of molybdenum was completed after oscillating the adsorbed molybdenum for a period of time between composite nanometer adsorbent and Mo (VI) at a certain speed. The concentration of molybdenum was determined by thiocyanate spectrophotometry. The result showed that under the condition of pH = 4.0, the adsorption effect of Mo (VI) on chitosanmodified magnetic nanoparticles was the best. The adsorption process accorded with the Langmuir adsorption isotherm model, and the high fitting degree with the quasi-second-order adsorption kinetic model accorded with chemical adsorption. Theoretical maximum adsorption capacity was 35.54 mg/g. The adsorption of Mo (VI) on chitosan-modified magnetic nanoparticles was still over 90% after 3 regenerations. Removal of Mo (VI) by chitosan-modified magnetic nanoparticles is quick and efficient. Its reusability is good. Its magnetic property is strong and it is convenient for solid-liquid magnetic separation. More importantly, our results provide a sustainable approach for removal of Mo (VI), chitosan-modified magnetic nanoparticles have more potential to be exploited and utilized for metal adsorption.