In this work the sol-gel technique was used to prepare indium oxide (IO), indium tin oxide (ITO) and indium zinc oxide (IZO) particles and deposited them on quartz substrate by dip coating technique. Many factors indicate as best parameters have been assumed (annealing temperatures and different compositions). The properties of In2O3, ITO and IZO particles were investigated and analyzed at different parameters: Structure and surface morphology of particles were characterized by X-ray diffraction (XRD), Atomic Force Microscope (AFM), Scanning Electron Microscopy (SEM), FT-IR and UV/visible measurements. The results of XRD for particles which annealed at (200, 400 and 600 ◦C) for 90 min lead to formation polycrystalline cubic phase of particles with high intensity of plane (222), the lattice constant increasing with increases the annealing temperature, the lattice constant was (10.08-10.16 A◦). The X-ray diffraction shown decreasing in the intensity of plane (222) and decreasing in the lattice constant with increasing the additive concentration of metallic oxides to reach (10.1-10.05 A◦), this may due to the ionic radius of the additive metallic oxides are smaller than In+3 ionic radius, which will lead to the decrease of the planar spacing of In2O3 crystal lattice. The results of atomic force shown increasing in the grain size with increases annealing temperature (88.8-96.6 nm), meanwhile the grain size decreasing with increases the additive concentration (ZnO or SnO2) (94.4-82.7 nm). The optical properties of In2O3 films at different annealing temperature and its composites with tin and zinc oxides annealed at 400 ◦C, were studied such as transmittance. The transmittance was measured over the wavelength range from (300 to 1100 nm) for all the films of indium oxide and its composites, the films of indium oxide have highly transparent reach to (74.8%), while ITO with 20% SnO2 thin film reach to (73.6%). The optical energy band gap increases with the annealing temperature in range (3.40 to 3.55 eV). Meanwhile decrease the band gab by additive metallic oxides (ZnO or SnO2) into indium oxide to reach (3.50 to 3.37 eV). The results of Hall measurements show that the In2O3 have a negative Hall coefficient (RH) values which confirm that the indium oxide is n-type for different parameters, the carrier concentration increasing with increases annealing temperature, the carrier concentration was (5.5*1011-1.9*1015 cm-3), also increasing with additive metallic oxides (SnO2 or ZnO) to reach (4.08*1012-2.8*1017 cm-3). From applied this materials in research for gas sensors towards CO, where the thin film of composite In2O3 with SnO2 at composition (80:20) mole ratio has high sensitivity compared with pure indium oxide, whereas pure indium oxide thin film sensitivity reach to 87% at annealing temperature 400 ◦C .