Recently, the surface mounting devices (SMD) have been rapidly developed for miniaturisation of electronic applications such as cellular phones, cameras, computers, etc. Low temperature sintering NiCuZn and MnCuZn ferrite was employed at most cases due to its co-firability with Ag (below 960OC).The purpose of this study is to fabricate NiCuZn and MnCuZn ferrite sintered body with high-strength and high-frequency magnetic properties. Following is the procedure: firstly, NiCuZn and MnCuZn ferrite powder were synthesized under CO2 atmosphere at 500 OC from the mixed doxalate synthesized by liquid phase deposition method; then a small amount of boric acid [H3BO3] was added to the powder, and the NiCuZn and MnCuZn ferrite powder compact were prepared with Newton press and CIP methods; finally, NiCuZn and MnCuZn ferrite sintered body was fabricated by sintering at 900 OC under CO2 atmosphere. The effect of boric acid additives on growth of particle and sintering temperature were discussed. The high frequency magnetic properties and density as well as bending strength of the NiCuZn and MnCuZn sintered magnet with various adding of H3BO3 as well as at various sintered temperatures were evaluated by using Impedance analyzer, TMA (Thermo Mechanical Analyzer), TEM (Transmission Electronic Microscopy) and 3-point bending test. From the evaluated results, the most suitable producing conditions were determined and NiCuZn ferrite with wider scope of high frequency and high bending strength were obtained.