Nonhygroscopic selenide of Ge0.35Ga0.05Se0.60 was introduced into the Li2S–P2S5 system by partially substituting P2S5 to form a new lithium ion solid electrolyte. And the electrochemical property of the as-prepared solid electrolyte was systematically studied. The optimal sample achieved a wide electrochemical window over 6.5 V and fairly high Li-ion conductivity of 1.5 × 10−3 S cm−1 at ambient temperature. And it is also verified that the studied electrolyte was much stable when contacts with lithium metal at 100 °C for 4 h. This new finding may provide an electrolyte material for developing all-solid-state lithium batteries.