Y2O3-ZrO2 (Y2O3 stabilized ZrO2) single-crystal fibers are promising candidates for developing ultra-high-temperature fiber-optic sensors; however, grown by conventional laser heated pedestal growth (LHPG) system, these fibers showed relatively low optical and mechanical qualities due to thermal stress caused by large temperature gradient during the growth, preventing the sensors from achieving high performance in our previous work. In order to grow high-quality Y2O3-ZrO2 single-crystal fibers with less stress, in this paper, according to the theoretical analysis, we have improved the growth system by adding an additional heating system, and the temperature gradient during growth has been reduced to an acceptable value. Five Y2O3-ZrO2 single-crystal fibers have been grown by the improved system; experimental test results showed that the optical and mechanical qualities of these fibers have been greatly enhanced, with which the ultra-high-temperature fiber-optic sensors with better performance could be developed.