This paper is a report of a study conducted on Structural, thermal and optical Properties of pure PMMA, pure PEO and PMMA-PEO-LiClO₄ polymer blend electrolyte thin films. These films were prepared using solution casting technique and characterized by X-ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). XRD analysis Observations confirmed that amorphous, crystalline and semi crystalline nature of pure PMMA, pure PEO and PMMA-PEO-LiClO₄ polymer blend electrolyte thin films the SEM micrographs suggest that the surface morphology of pure PEO changes from smooth to rough when PMMA and LiClO₄ added to PEO polymer, which shows the interaction/ interface between the two polymers and polymer blend electrolyte due to cross – linking. Glass transition (T_g) and melting temperatures (T_m) of pure PMMA, pure PEO and PMMA-PEO-LiClO₄ polymer blend electrolyte thin films were confirmed by DSC analysis. FTIR spectra confirmed that complex formation and interaction among PMMA, PEO polymers and LiClO₄ salt.