The morphology, chemical composition of the deposits in the inner wall of the bubble were analyzed by optical polaring microscope, scanning electron microscope-energy spectrometer. Gas composition in the bubble were analyzed by bubble analysis mass spectrometer. Cause of the bubble was determined: SiC was contained in the new energy-saving silica brick used in furnace crown, which was partially broken during the temperature rise, then the broken brick slag fell into the furnace before adding broken glass and batching. With the liquid glass moving to the end of the working part, the broken brick slag continuously react with liquid glass to form bubbles. Finally, a solution to the bubble defect was proposed, and the application effect is ideal.