High quality Y2O3-ZrO2 single crystal rectangular waveguides had been developed for high-temperature sensing applications. The waveguides were fabricated from bulky Y2O3 stabilized ZrO2 single crystal by precise cut and fine polish. Three rectangular waveguides with cross-section larger than 1mmx1mm and length of 45mm 65mm were obtained. They showed much better optical properties than Y2O3-ZrO2 single crystal fibers grown for fiber-optic sensing in previous work, optical losses of these waveguides were lower than 0.03dB/cm at wavelength of 900nm, and they were able to endure temperature as higher as 2300 degree(s)C. All of them survived a 10g vibration test with average STF (strain to failure) of about 0.25%. Experimental results show that, these waveguides are promising for fiber-optic sensing for temperature above 2000 degree(s)C.