Abstract: Mn-Co-Ni-O spinel, owing to its low resistivity and large temperature dependent resistivity, is an attractive ternary system for thermistor applications and infrared detecting bolometers. Mn1.56Co0.96Ni0.48O4 (MCNO) polycrystalline films for infrared detection were successfully deposited on amorphous Al2O3 substrates by radio-frequency (RF) magnetron sputtering. Energy dispersive spectroscopy (EDS) indicates, for all the MCNO films, that the deviations of metallic element composition rank less than 5% comparing to the target. Structural, electrical, optical properties of MCNO films annealed at 750℃ were also investigated. X-ray diffraction shows the 750℃ annealed sample has a single cubic spinel phase, and the film is of favorable crystallization and compact density. The conduction mechanism of MCNO thin film follows the small-polaron hopping model, and the hopping type is variable-rangehopping (VRH) at 240-330 K. The TCR and the activation energy of MCNO films at room temperature (300 K) is 0.297 eV and-3.83%K-1, respectively. Also, the absorption coefficient has a relatively high value in the region of ultraviolet-visible and the indirect band gap is about 0.61 eV.