In order to increase the magnetic fluids in target-based cancer treatment, the Cu2+ has been studied in this study. The Fe3O4 and Cu0.1Fe0.9O•Fe2O3 magnetic nanoparticles were prepared by ultrasonic emulsion method, and then disperse them into water with sodium dodecyl benzene sulfonate (SDBS) as surfactants to make magnetic fluids. The cubic inverse spinel structure of Fe3O4 and Cu0.1Fe0.9O•Fe2O3 nanoparticles were analyzed by X-ray diffraction technique (XRD).The saturation magnetization of Fe3O4 and Cu0.1Fe0.9O•Fe2O3 were 79.55 emu•g-1 and 75.90 emu•g-1 by vibrating sample magnetometer (VSM). The morphologies of nanoparticles were observed by transmission electron microscope (TEM). The particle size was uniform 10-20 nm, and their shape was approximately spherical. The Cu0.1Fe0.9O•Fe2O3 magnetic particle functional group and the surface of particle coated with SDBS have been detected by Fourier Transform Infrared Spectroscopy (FT-IR). The magnetic fluids with a high saturation magnetization and stability have been prepared successfully in this study.