Silica/mullite ceramic cores were prepared using fused mullite and sintered mullite powders as mineralizer in silica-based ceramic cores, and compared with ceramic cores without mineralizers. Compared to fused mullite, the sintered mullite powders have large contents of impurities including alkali metals and alkaline-earth metals, and highly promote the crystallization of silica glass and significantly decreased the activation energy for crystallization; however, the excess impurities acted as network modifiers, and increased the creep deformation at high temperature. The fused mullite can not only improve the crystallization of silica glass, but also benefit the resistance to high temperature deformation. The ceramic cores with 10wt% fused mullite show linear shrinkage of 0.73%, porosity of 30.5%, room temperature strength of 18.9 MPa, high temperature creep deformation of 0.3 mm, which will meet the demands for hollow blade casting.