Abstract: SiO2-TiO2 planar optical waveguides were prepared with the sol-gel method. The thermal properties of SiO2/TiO2 sol-gel were analyzed with differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA). The morphologies of planar waveguides were characterized by SEM and AFM. The propagation loss of the planar optical waveguide at 1550nm was measured. The experimental results demonstrate that the gel thin film with the drying processing at 200℃ in 30min presents the porous structure, and for the unsymmetrical planar waveguide, there is a light flux cut-off thickness for a core layer. When the thickness of SiO2-TiO2 core layer is 0.5 μm, the cladding thickness should be at least 6 μm to prevent 155 0 nm light from propagating into the substrate of monocrystalline silicon. At present, the minimum propagation loss of the planar optical waveguides at 155 0 nm is 0.34 dB/cm.