Designing Na-ion solid electrolytes (SEs) of high ionic conductivity and excellent chemical/mechanical compatibility with cathode materials remains challenging for all-solid-state Na-ion batteries (ASSNIBs). In this study, we successfully design and synthesize a novel amorphous NaTaCl6halide SE with unprecedented ionic conductivity of 4 × 10−3S cm−1at room temperature. The exceptional ionic conductivity arises from a unique reconstructed amorphous poly-(TaCl6) octahedra network with weakening Na-Cl interactions through high-energy mechanochemical reactions. Notably, the amorphous NaTaCl6halide SE exhibits remarkable mechanical deformability, chemical/electrochemical stability, and outstanding electrochemical performance when coupled with the Na3V2(PO4)3cathode in ASSNIBs, resulting in a remarkable initial Coulombic efficiency of 99.60%, excellent rate performance (85% capacity retention at 2 C), and stable long-cycling profiles (81%/95%/98% capacity retention after 4,000/600/1,500 cycles at 3/1/0.5 C). This discovery of superionic amorphous Na-ion halide SEs opens a promising avenue for advancing high-performance ASSNIBs.