The microstructure of the gold decoration layer of bone china was investigated to pinpoint the cause of the gold cracking occurring during the manufacture of high-quality bone china. Using cross-sectional TEM analysis, it was observed that SnO2 crystals from the matting agent underneath the gold underwent abnormal growth. When the few SnO2 crystals grew excessively, the matting oxide burst through the gold layer, resulting in the gold cracking. From this study, we conclude that control of the size distribution of SnO2 crystals is very important keep a high-quality gold layer.