Solid-state glass electrolyte, xLi2O–(1− x)(yB2O3–(1− y)P2O5) glasses were prepared with wide range of composition, i.e. x =0.35–0.5 and y =0.17–0.67. This material system is one of the parent compositions for chemically and electrochemically stable solid-state electrolyte applicable to thin film battery. The purpose of this study is to seek the best composition among the various compositions for the deposition of thin film electrolytes. Lithium ion conductivity of Li2O–B2O3–P2O5 glasses was characterized by ac impedance technique. The ionic conductivity of the electrolyte at room temperature increased with x and y. The maximum conductivity of this glass system was 1.6×10−7 Ω−1 cm−1 for 0.45Li2O–0.275B2O3–0.275P2O5 at room temperature. It was shown that the addition of P2O5 reduces the tendency of devitrification and increases the maximum amount of Li2O added into glass former without devitrification.