We studied the effects of iron-deficient, stoichiometric and iron-excessive compositions on the phase formation, crystal structure, grain growth and magnetic property of NiCuZn ferrites. As the Fe2O3 ratio increased from iron-deficiency 47.0mol% to iron-excess 54.0mol%, the X-ray diffraction peaks initially shifted towards lower angle and then moved to higher angle. Correspondingly, an initial increase in lattice parameter followed by a subsequent decrease was observed. The lattice parameter showed a maximum 8.396Å when the Fe2O3 ratio was 49.0mol%. When the system was iron-deficient, ZnO phase was detected in addition to the spinel phase. However, equimolar and iron-excessive compositions exhibited a single spinel phase. As the content of Fe2O3 increased, the grain size, density, saturation induction and initial permeability first increased and then decreased. Core losses at 50kHz and 150mT, however, changed in the opposite way. Finally, NiCuZn ferrite with an equimolar composition (50.0mol%) showed the highest initial permeability (1467), highest saturation induction (361mT) and lowest core losses (234kW/m3).