NiCuZn ferrite powder with fine particles size distribution and high activity was synthesized by chemical co-precipitation. The effects of synthetic conditions, such as reaction temperature, stirring speed and flow rate of salt solution, on the precursor particle size of NiCuZn ferrite were investigated. The samples prepared at the optimal condition were characterized by XRD, TEM, laser particle size analyzer (LPS), precision impedance analyzer and vibrating sample magnetometer (VSM). The results show that the powder is possessed of pure spinel, the particle size of about 30 nm, the average grain size of 11 nm, while the synthetic conditions are the reaction temperature for 70 °C, the flow velocity of the salt solution for 0.5 mL/min, stirring speed for 300 r/min. NiCuZn ferrites, presintered at 500 °C and sintered at 900 °C, have achieved excellent magnetics. The relative density of sample is 98%, the initial magnetic permeability is 200, quality factor is 150 and the cut-off frequency is 70 MHz