Abstract: X-ray micro computed tomography (Micro-CT) has emerged as a crucial methodology for revealing microstructure-property relationships in materials science and related disciplines, leveraging its unique advantages of non-destructive, three-dimensional (3D), and high-resolution imaging. This review systematically outlines the technical framework and frontier advancements of Micro-CT, contrasting laboratory-based X-ray sources with synchrotron radiation sources. Key emphasis is placed on the advancements in four-dimensional (4D) in-situ testing for tracking damage evolution, the breakthroughs in laboratory X-ray diffraction contrast tomography (Lab-DCT) for 3D crystallographic characterization, and the frontier applications of deep learning in image enhancement and automated segmentation. Finally, the paper concludes by charting the technological evolution of Micro-CT from qualitative "morphological description" to quantitative "mechanism prediction," aiming to provide high-fidelity 3D characterization support for the design optimization and service reliability evaluation of advanced high-performance composites.