This paper investigates the causes of porcelain bushing burst failure in high-voltage gas-insulated switchgear(GIS)at a 220 kV substation.Macroscopic and dimensional inspections，porosity tests，porcelain analysis，and phenolphthalein tests reveal that the fracture morphology of the porcelain bushing resembles that of mechanical bending failure.While the porcelain body itself shows no abnormalities，significant eccentricity in the bonding of the bushing is observed，with traces of water seepage，moisture absorption，and carbonization in the cement adhesive.The study discusses the effects of axial displacement of the GIS bus tube during cold wave conditions and the impact of bus tube rotation under solar radiation during heating on the porcelain bushing，verified through simulation.Results indicate that the center of gravity of the bushing shifts due to cementing eccentricity.Rapid cooling and subsequent heating during the cold wave accelerate aluminum alloy bus tube displacement，causing angular deformation.The resultant force concentrates at the weak section of the bushing with cementing eccentricity，ultimately leading to the porcelain bushing burst.