Novel polymer electrolyte aimed for electrochromic display was prepared by polyvinylbutyral (PVB), imidazole (Imz) and tetrabutylammonium perchlorate (TBAP). The polymer electrolyte was designed to have large difference in ionic conductivity between high and low temperature. This would be effective to inhibit the spreading of electrochromic images at ambient temperature due to cell formation between colored and uncolored parts through ionic conductor. Namely, this polymer electrolyte enables writing and erasing at high temperature due to high ionic conductivity, and the image is expected to be preserved without change and spreading at ambient temperature due to low ionic conductivity. In the results, the ionic conductivity in the polymer electrolyte was dramatically increased above the quasi-melting point of the component. Optimum ratio between Imz and TBAP content should be required to obtain higher ionic conductivity at high temperature. Ionic conductive properties of the polymer electrolyte were mainly studied and discussed.