Manganese oxide thin films were deposited on glass substrates by resistive evaporation at room temperature. The layers were produced with electron gun evaporation method under ultra-high vacuum condition. Thickness of the layers was measured 60 and 120 nm, by a quartz crystal method. Deposition conditions such as deposition rate, vacuum pressure, incidence of angle and substrate temperature were the same for all layers. After producing pure manganese oxide layers a post-annealing method was used in the presence of a uniform oxygen flow of 300 (sccm) and at 320 oC annealing temperature. Optical reflectance and transmittance of the layers were measured in the wavelength of 350–850 nm by a spectrophotometer. Kramers–Kronig relations were used to calculate the optical constant. The influence of annealing temperature and oxygen flow on optical properties is investigated. It was found that film thickness and deposition angle plays an important role on the nanostructures as well as optical properties of layers and cause significant variations in behavior of thin titanium oxide films. The physical properties of materials were characterized by X-ray diffraction (XRD), FE-SEM, AFM, EDX, and UV-Vis techniques.