Bubbles are one of the main defects of electronic glass substrates, especially the bubbles with diameter of greater than 0.3 mm, which will destroy the preformance of electronic glass and result in decrease of the yield or even a large number of waste products in following processing of the glass substrates. This is the quality defect with a high frequency. The measures such as improving batching control and the constant water in the batches, improving the water box at feeder inlet to keep the furnace pressure stable, and optimizing the heat load distribution have promoted to enhance the refining efficiency and reduce bubble defects.