Ceramic cores are key to forming a cooling structure within the hollow blade cavities. The use of stereolithography (SL) 3D printing technology eliminates the need for moulds, facilitating the preparation of complex-shaped ceramic cores. In this study, silica-based ceramic cores incorporating nano-3YSZ (3mol.% yttria stabilised zirconia) and micron-sized Y2O3 were prepared via SL 3D printing ceramic technology to promote the formation of cristobalite and ZrSiO4, thereby improving the high-temperature properties. The flexural strength at 25 °C and 1,500 °C, deflection at 1,500 °C, shrinkage rate, and porosity of the core samples sintered at different temperatures (1,170 °C, 1,185 °C, 1,200 °C, 1,215 °C, and 1,230 °C) were tested and investigated. The mechanism underlying the high temperature performance of the cores was elucidated through analysis of cross-sectional morphology, element distribution, and phase constitution of the samples. As the sintering temperature increases, the shrinkage and flexural strength at 25 °C of the core rise, while the open porosity and deflection at 1,500 °C decrease. When the sintering temperature reaches 1,200 °C or higher, the 1,500 °C flexural strength can be measured, which increases as the sintering temperature rises. The core exhibits excellent creep resistance when sintered at temperatures of 1,200 °C and above. Considering the comprehensive performance requirements for the core, the sintering temperature of 1,200 °C was selected. At the sintering temperature of 1,200 °C, the core exhibits shrinkage rates of 3.76% (X), 3.38% (Y), and 3.95% (Z), alongside a flexural strength of 9.01 MPa at 25 °C and 32.15 MPa at 1,500 °C, and an open porosity of 26.39%. The deflection of the core at 1,500 °C is 0.15 mm, which helps to maintain the dimensional stability of the ceramic core during casting. XRD results indicate that samples fractured after 25 °C flexural strength test still contain amorphous quartz glass, alongside substantial quantities of yttria stabilized zirconia and Y2O3. Samples fractured after 1,500 °C flexural strength test exhibit significant crystallisation of amorphous quartz glass into cristobalite, with silica and 3YSZ combining to form ZrSiO4. Y2O3 as a network modifier of the glass network destroys the bridging oxygen in the silica-oxygen bond, thereby reducing the energy required for glass crystallisation and promoting the crystallisation reaction of quartz glass to form cristobalite. In addition, nano-3YSZ combines with SiO2 at high temperatures to form ZrSiO4. Since cristobalite and ZrSiO4 are crystals, both of them have strong creep resistance, thus improving the high temperature flexural strength and deformation resistance of the ceramic cores.