High quality Y₂O₃-ZrO₂ single crystal rectangular waveguides were fabricated from bulky Y 2O 3 stabilized ZrO 2 single crystal by precise cut and fine polish with cross section larger than 1mm×1mm and length of 45mm～65mm. They show much better optical properties than Y 2O 3 ZrO 2 single crystal fibers grown by the conventional LHPG system, optical losses of the waveguides are lower than 0.03dB?cm at wavelength of 900nm, the damage thresholds are 0.98 MW?cm 2 for 1.06μm Nd:YAG laser pulses, and they are able to endure temperature as higher as 2300℃. Experimental results show that these waveguides are promising for fiber optic sensing applications at temperature above 2000℃.