The preparation process of single polarization α-phase LiNbO3 optical waveguide is studied using dilution of stearic acid and high temperature proton exchange technology. A high temperature sealing device is developed. A method by increasing vapor pressure to achieve the 350 ℃ proton exchange is proposed. Waveguide refractive index distribution is tested by using prism film coupling m-line technology and the statistical iterative method fitting. Crystal phase is analyzed by testing infrared absorption spectrum technique. The experimental results show that α-phase LiNbO3 optical waveguide can be produced under the conditions of the stearic acid doped with 1.1% lithium stearate mass proportion as buffer proton source and 350 ℃/6 h high temperature proton exchange. Single mode α-phase LiNbO3 optical waveguide at 632.8 nm wavelength can be produced under the conditions of the same temperature, time and the dilution of 1.3%.