All-solid-state batteries (ASSBs) emerge as a current research hotspot due to their high safety, extended cycle life, and elevated energy density. Understanding the intrinsic relationship between the structure and performance of solid electrolytes (SEs), along with interfacial charge transport properties, is crucial for the stable operation of ASSBs. Synchrotron radiation (SR) technology provides a significant support for analyzing the composition-structure-performance relationship in ASSBs due to its high brightness and adjustable energy. It is especially applicable to investigate the dynamic evolution of materials and interfaces, charge migration, and failure mechanisms during battery cycling.The review outlines the classification, principles, and applications of synchrotron radiation X-ray (SR-X) technologies, i.e., synchrotron X-ray diffraction (SXRD), X-ray absorption spectroscopy (XAS), synchrotron X-ray photoelectron spectroscopy (SXPS), and synchrotron X-ray microscopy (SXM). The focus is on the advantages of SR in elucidating local structures, chemical states, and microstructures.The review also represents the applications and progress of SR-X in ASSBs. Initially, it highlights progress on using SR-X to explore the composition-structure-property relationships in SEs and monitor structural evolution and charge mobility during ASSB operation. The review represents the use of SR-X in detecting SEs/interfaces, examining changes in interface structure, composition, and morphology during battery cycling, with a focus on SEs/cathode and SEs/anode interfaces.Summary and prospectsThis review represents recent advancements in the application of SR-X techniques for studying SEs and their interfaces, emphasizing their unique capabilities in resolving local structures, chemical states, coordination environments, and interfacial heterogeneities, while elucidating the failure mechanisms of ASSBs. To advance the practical implementation of ASSBs, the future development on SR-X technology should focus on three key areas, i.e.,1) Advancing in-situ SR-X techniques with higher temporal and spatial resolution. Real-time monitoring of the dynamic evolution of solid-solid interfaces during battery operation is essential for capturing transient phenomena in chemical and electrochemical reactions. An atomic-scale resolution will enable a detailed investigation of microstructural and chemical properties, particularly for sensitive elements like Li and Na. 2) Integrating SR-X with complementary techniques for multiscale analysis. Combining methods such as SXM and XAFS can provide synergistic insights into the microstructure and chemical composition of materials, offering a comprehensive understanding of both heterogeneous and average properties in ASSB components. 3) Developing in-situ electrochemical cell designs compatible with SR-X techniques. These configurations should ensure sufficient signal strength for characterizing material components and interfaces, while maintaining a typical electrochemical behavior under synchrotron beamline conditions. Advancing these aspects will unlock the full potential of SR-X techniques, driving the commercial viability of ASSBs.