As a new class of multi-principal component oxides with high chemical disorder, the structure and properties stability/tunability of high-entropy oxides (HEOs) is of great interest and importance but remains unclear. Here, using in situ synchrotron radiation X-ray diffraction, Raman spectroscopy, ultraviolet-visible absorption spectroscopy, and ex-situ high-resolution transmission electron microscopy, we confirmed the existence of lattice distortion in the crystalline structure of a HEO according to the deviation of bond angles from the ideal values, and discovered an unparalleled pressure-induced continuous tuning of lattice distortion (bond angles) and band gap. As continuous bending of bond angles, pressure eventually induced breakdown of the long-range connectivity of lattice and caused amorphization. The amorphous state can be partially recovered upon decompression forming glass-nanoceramic composite HEO. These results revealed the unexpected flexibility of the structure and properties of HEOs, which could promote the fundamental understanding and also applications of HEOs.