Wetting of molten SAT(Sn3.5Ag-(2, 4)Ti) alloys on typical silica substrates (vitreous silica, sintered quartz, translucent fused silica and microlite glass) and on the surface of the interfacial precipitation layer was investigated by a modified sessile drop method at 800 °C under high vacuum. After cooling the wetting couples, both TiO2-x and a small amount of Ti5Si3 were precipitated at the interface and Sn5Ti6 - segregation above TiO2-x layer was observed. However, this does not indicate that the precipitated TiO2-x determines the final wettability, rather the isothermal wetting process in which Ti is segregated and adsorbed at the solid/liquid interface, significantly improving the wettability. Among them, vitreous silica and microlite glass in one group; sintered quartz and translucent fused silica in another group, have the similar interfacial microstructures, which linked to the difference in macroscopic wettability and apparent spreading dynamics.