The ceramic core was prepared using the hot injection method, where quartz glass powders were used as original materials, zircon as additive, and the ceramic casting wax as the plasticizer. The purpose is to test the changes in the properties of cores and the effect of zircon content on the properties of silica-based ceramic core. It was learned that the zircon additive has no obvious effect on core crystallization. Zircon, which has high melting point and stability, did not react with silica and could reduce the viscous flow of quartz glass and the degree of sintering of the core. As a result, the more zircon was added, the lower the shrinkage and room temperature strength were, and the greater the porosity was. A small amount of zircon, which was distributed in the quartz glass matrix, contributed to strengthening the matrix and also improved the high temperature strength of the core. When the content of zirconium silicate was high, the content of quartz glass decreased, and the content of quartzite which resulted from crystallization of quartz glass decreased as well, and this resulted in the lowering of high temperature strength. The high temperature deflection of the core decreased with the increase of the zircon content because zircon could reduce the viscous flow of quartz glass at high temperature.