Abstract: Ti is an important active element to join SiO_2f/SiO₂ composite materials. Therefore, the bonding mechanism of Ti and SiO₂ was studied by using first principle calculation. Two kinds of interfaces with different termination and stoichiometric ratio were studied by the results of work of separation (W_sep), electron behavior and interface energy. It is found that in the O-terminated interface, Ti and O atoms form a strong ionic-covalent bonding, resulting in the largest W_sep of 8.99 J/m². In the Si-terminated interface, Ti and Si atoms form covalent-ionic bonding, and the W_sep is 2.65 J/m². At the temperature of 1 173 K, when the activity of Si is larger than e⁻³⁵, the interface of Si-terminated interface is more lower. The Ti-Si compounds are more favored at the interface. When the activity of Si is smaller than e⁻³⁵, the O-terminated interface is more stable in thermodynamics and the Ti-O compounds are more favored at the interface. After Si in SiO₂ in replaced by Ti, Si will diffuse into the solder and react with Ti in the solder to form Ti-Si compounds, so the interface struture is SiO₂/Ti-O compound/Ti-Si compound/solder.