Ion-conducting chalcogenide glass is a promising solid electrolyte with excellent conductivity and energy density for all-solid-state batteries. A suitable ionic channel for carriers in the amorphous network is urgently needed. In this work, the structural evolution of co-doped metal cations (Ge and Ga) in the glass matrix and its influence on electrochemical behavior were studied using a series of GexGa16-xSb64S128-40AgI glass samples. The macroscopic properties of samples were examined by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Raman tests. The electrochemical behavior of samples was investigated by AC impendence spectroscopy and cyclic voltammetry (CV) measurement. Furthermore, a deliquescence experiment was applied for the chemical stability test of glass samples. The ionic conductivity of samples was developed by adding Ga components. Notably, the electrochemical window of electrolytes was remarkably wide at approximately 5 V. The resistance of samples to humidity was characterized by the decreased Raman peaks. Analysis results show that the Ga-related bonding structure evidently increased the chemical stability compared with the non-Ga sample. This work provides an insight into the effective and stable ions transport, especially in the Ge(Ga)SbS glass system. These results promote the further investigation of sulfide solid electrolytes and practical application of all-solid-state batteries.