The effect of gallium oxide on densification of low-dielectric binary glass composite containing a low-softening-point borosilicate glass (BSG) and a high-softening-point high silica glass (HSG) has been investigated. By doping 2-10 vol% gallium oxide into the binary glass composite, the densification is dramatically reduced, but the activation energy of densification at a given densification is significantly increased. The above results are attributed to an interfacial reaction between alkali ions from low-softening-point BSG and gallium ion from gallium oxide. The interfacial reaction takes place at the interface of BSG and gallium oxide and forms a reaction layer with a composition rich in alkali and gallium ions, which continuously reduces the alkali ion content in the BSG and causes a rise in the viscosity of BSG during firing. Because the rate-limiting step during densification of the binary borosilicate glass is the viscous flow of BSG, a higher viscosity of BSG slows down the densification kinetics and increases the activation energy of densification.