Optical properties of solid polymer electrolyte films based on polyvinyl alcohol (PVA) with different concentration of cobalt nitrate Co(NO3)2 (3-12) wt% have been studied. The parameters such as refractive index, extinction coefficient, and optical energy gap were investigated by using the absorbance measurement from UV-visible spectrophotometer in the spectral range (190-790) nm. This study reveals that the optical properties of PVA are affected by salt concentration, where the absorption increases and absorption edge decreases as Co(NO3)2 concentration increases. The refractive index, and extinction coefficient values were found to increase with increasing Co(NO3)2 percentage. The optical energy gaps have been investigated and showed a clear dependence on the Co(NO3)2 concentration. The interpreted absorption mechanism is both direct- and indirect- electron transition, and it was found to be decreasing with increasing Co(NO3)2 concentration. The single oscillator model has been used to analyses the dispersion behavior of the refractive index, and the dispersion parameters are calculated.