Pure and Antimony Trioxide Sb2O3 doped PMMA films were prepared by the casting method. Optical absorption measurements in the wavelength range 200-800 nm were studied by using a computerized UV-Vis spectrophotometer (Shimadzu UV-1601 PC) and these confirmed that PMMA films have a direct band gap that decreases from 5.15 to 4.66 eV as the doping concentration increases to 5wt%. The increase in the density of localized states from 8.9 to 74.5 meV causes an expansion in the Urbach tail and consequently decreases the energy gap. The dispersion of the refractive index was analyzed using the concept of a single oscillator. The values of the single oscillator energy were 32.70, 13.59, 7.06, and 4.58 eV, while the dispersion energy values were 4.36, 49.04, 21.76 and 14.15 eV for the pure, and 3%, 4% and 5% Sb2O3 for the doped PMMA films respectively. The single-term Sellmeier were determined, and the average oscillator position was investigated, the value of which decreased with increasing doping concentration. The value of average oscillator strength increased with increasing Sb2O3 concentration to 5wt%. Skin depth and optical conductivity could be calculated, and results show a decrease in Skin depth with an increasing impurity percentage, but an increase of optical conductivity with greater impurity