Magnetic Ni-Zn ferrite nanoparticles were prepared via the citrate-gel process, their microstructure and the properties were characterized by XRD, VSM, SEM, and TEM techniques. For smaller grain size and larger specific saturation magnetization, the preparation technology for magnetic Ni-Zn ferrite nanoparticles was optimized, and the optimization conditions followed as: the molar ratio of Ni, Zn and Fe was 1:1:4, citric acid was applied according to the mole ratio of 1:1 for citric acid and metal, the solvent of 100 mL was the mixed liquor of alcohol and water with volume ratio of 1:1, pH value was 1, reaction time was 24 h, the calcination temperature was 400 °C, and the heating rate was 3 °C/min. The average crystallite size of the as-prepared Ni0.5Zn0.5Fe2O4 nanoparticles calcined under the optimization conditions was around 14 nm, and the specific saturation magnetization was about 46 emu/g.