Pure and Antimony Trioxide Sb2O3 doped PMMA Films were prepared by casting method. Optical absorption measurements in the wavelength range (200-800) nm were studied and confirmed that PMMA films have an direct band gap that decreased 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 expanding in the Urbach tail and consequently decreases in 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 07.23, 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 doped PMMA films respectively. The single-term Sellmeier were determined, the average oscillator position was investigated and its value decreased with increasing doping concentration. Values of average oscillator strength was increased with Sb2O3 concentration to 5wt%. Skin depth and optical conductivity could be calculates where results show a decreasing in Skin depth with impurity percentage while increasing of optical conductivity with this percentage.