Scoured frequently by flame and affected by temperature gradient, the flat skewback on the flat arch of the crater (outlet) of the 600 T float glass production line which had been running for 4 years was defective in thermal shock stability. Most of the zirconium corundum bricks (AZS33 #) on skewback of the crater (outlet) of the chauffer fell off, a defect that was approximately 1,800mm long, about 300mm wide, about 300mm deep was formed. Flame soared from the joint between the flat arch and the slope arch, and the skewback beam turned red, so the structure safety of glass the furnace was affected seriously. By using the ceramic welding technology combined with high temperature furnaces periscope, our company conducted thermal repair for flat arch bricks, which then maintained safe operation for 25 months.