In this research, Cu_0.5Zn_0.5Fe₂O₄ nanoparticles were prepared by citrateprecursormethod and under air-ambient annealing at 200, 400, 600^°C. The structural features of samples were investigated by X-ray powder diffraction and FT-IR spectroscopy. The structural characterization of compounds, using X’Pert package and Fullprof program, is evidence for formation of a cubic structure (Fd-3m space group) with no presence of impurity phase that is emphasized by FT-IR data. Calculated values of crystallite size and unit cell parameter show a minimum for the sample annealed at temperature 200˚C. Band gap energies of samples have been estimated using absorption coefficient. under similar reaction conditions, the catalytic results show that the sample annealed at temperature 200˚C is the best catalyst for the CO and C₂H₆ oxidation due to smaller crystallite size.