Nanostructured ferrites possess more advantages than the conventional ferrite materials and have been a research focus recently. In this work, a series of nanostructured Ni0.5Zn0.5Fe2O4 were synthesized by a citrate reaction method followed by calcining at various temperatures with the goal of obtaining pure phase Ni0.5Zn0.5Fe2O4 nanoparticle while keeping the size small. X-ray diffraction, transmission electron microscopy, SQUID magnetometry and Mössbauer spectroscopy (ME) have been employed to characterize the crystal structure, phase homogeneity, particle size, the conditions for reaction completion, and the magnetic properties. The results show that the saturation magnetization Ms at both 10K and 300K increase with increasing calcination temperature Tca, but particle size also increases with Tca. Three factors, the incomplete reaction for ferrite phase formation, the surface effect and superparamagnetic behavior, are found to be responsible for low Ms values at lower Tca. Based on a detailed analysis of nanostructure and magnetic properties in ferrites, the optimal conditions for synthesizing nanostructured Ni0.5Zn0.5Fe2O4 have been established.