The low-energy dynamics of Ag-based superionic conducting glass system has been investigated using the inelastic neutron scattering measurements. A clear correlation between the intensity in low-energy region and the dc ionic conductivity was found. The cross-linking factor is considered to be the network expansion by salt doping. Detailed investigations of low-energy dynamics both for varied superionic conducting glasses and insulator glass have proved that the peculiar Q dynamics beyond around 2 Å -1 is a characteristic feature only in superionic conducting glass.