Abstract: Fe₃O₄ magnetic nanoparticles (MNPs) have large specific surface area, high adsorption capacity, and can be separated conveniently from liquid with outer magnetic field. The crown ether has the ability to select coordination of uranyl ion. In the study, the magnetic 18-crown-6/LA/Fe₃O₄ composite nanoparticles which combined the characteristics and advantages of both the crown ether and Fe₃O₄ MNPs were prepared. The nanocomposite was characterized by infrared radiation (IR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), vibrating sample magnetometer (VSM) and thermal gravimetric analysis (TGA). The results indicate that the size and the saturation magnetization of the nanocomposite are 12-23 nm and 56.34 emu/g, respectively. Preliminary experiments for the adsorption of uranyl ion were carried out. In the selected conditions, the equilibrium adsorption rate reaches 95%. Meanwhile, the magnetic nanocomposite can be recycled and enriched easily.