Polishing lathe flame polishing is a process of local heat treatment on the surface of the preform. The heating of the surface of the fiber preform leads to a decrease in the viscosity of the local glass. Which resulting in local remelting of the surface layer. However, the temperature inside the fiber preform is lower than the plastic deformation temperature, so it is not affected. Due to the fact that flame polishing only generates high temperatures on the surface of the product and completes the entire process at a fast speed. Flame polishing can improve surface roughness, eliminate cracks, and achieve the same goal as acid washing.