Silica sol is a high-quality water-based binder commonly used in investment casting. Since it was introduced into investment casting in the 1960s, the process technology of shell making has been continuously improved, and the relevant theory has also developed rapidly. However, most of the publicly published literature is about the control of the shell making process and process parameters and the selection of refractory materials, while there is no relevant report on the analysis of the microstructure of the shell in the investment casting process.