Abstract. XAFS measurements near the Zr K-edge for the P2₁/c and Pbca ZrO₂ phases with particle size of 62 nm and 0.50 μm were performed under pressure up to 7.8 GPa using a multi-anvil high-pressure device and synchrotron radiation at BL14B1, SPring-8, Hyogo. XANES spectra change gradually near the phase transition region of 3.0–4.8 and 4.8–7.8 for bulk and nano particles. The second-nearest Zr-Zr distance in nano particle is 0.02 Å longer than that in bulk particle. It was found that the nano particle is more compressible comparing with the bulk particle and transforms to the Pbca phase at certain specific Zr-O and Zr-Zr distances. The magnitudes of σ2 for Zr-Zr distance in the nano particle are significantly larger because of the static disorder near the surface.