This research focuses on characterizing elastic properties of Zircaloy cladding tubes at high temperature environment up to 295°C. A laser ultrasound technique (LUT) is used to measure the dispersions of guided waves propagating along the axial direction of the cladding tubes at different temperature environment. It is shown that the LUT is able to measure the dispersion curve of Zircaloy in the elevated temperature environment. Then an inversion procedure is used to determine elastic constants of the Zircaloy tubes at high temperature from the measured dispersion spectra of guided waves. The dispersion spectra shift towards the direction of lower frequency and lower velocity while the temperature increase. The Young's modulus is found to decrease linearly as the temperature increasing. This method is potentially useful to probe the material properties at high temperature environment in a remote and nondestructive way which is desired in nuclear power industry.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.