This study investigates the fabrication process of Zn-diffused ridge waveguides in periodically poled magne-sium-doped lithium niobate (PPMgO: LN). A controlled variable method is used to study the effects of diffusion tem-perature, diffusion time, ZnO film thickness, and barrier layer thickness on the surface domain depolarization and wa-veguide quality of PPMgO: LN. A special barrier layer is proposed that can automatically lift off from the sample sur-face, which increases the depth of Zn doping and reduces the surface loss of the waveguide. By optimizing the process parameters, we fabricate Zn-diffused PPMgO: LN ridge waveguides with a length of 22.80 mm and a period of 18.0 μm. The above waveguides can make a second harmonic generation (SHG) at 775 nm with an output power of 90.20 mW by a pump power of 741 mW at 1 550 nm. The corresponding conversion efficiency is 3.160%/W?cm2, and the waveguide loss is approximately 0.81 dB/cm. These results demonstrate that high-efficiency devices can be ob-tained through the fabrication process described in this paper.