AbstractIn this study, a self‐developed online test platform for high‐temperature mechanical properties was utilized to test the tensile properties of three continuous ceramic fibers from room temperature to 1 000°C. It was observed that the tensile strength of all tested continuous ceramic fibers decreased significantly with increasing temperature. Specifically, significant peeling of the surface organic coating from room temperature to 400°C, inherent and newly formed defects exposed from 600°C to 1 000°C contributed to the decrease in tensile strength. More importantly, compared with room temperature, the strength of the silicon carbide fibers and the alumina fibers remained 29.7% and 20.2% respectively when stretched online at 1 000°C, while the quartz fibers dropped to 4.3% dramatically. These findings contribute valuable data for the potential application of ceramic fiber filaments as flexible thermal protection materials.