This study presents a comprehensive assessment of the preservation state of three coffin wood planks excavated from the Northern Wei tomb at Zhijiabu, Datong, Shanxi, through the application of multidisciplinary analytical methods. After identification of the wood species, the ultrastructure of the samples was examined using focused ion beam-scanning electron microscopy (FIB-SEM). In addition, chemical compositional changes were investigated using Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD), and solid-state carbon nuclear magnetic resonance (¹³C-NMR). To further characterize changes in wood porosity, micro-computed tomography (micro-CT) was employed to obtain detailed two-dimensional and three-dimensional structural data. The results identified the wood as cypress. Compared with modern intact cypress, all archaeological samples exhibited particulate surface deposits, cracks, holes, and significantly increased porosity. FIB-SEM observations revealed severe damage to the cell walls and intracellular residues, indicating the combined effects of brown rot, soft rot fungi, and erosive bacteria in the degradation process. Chemical analyses showed substantial degradation of hemicellulose, reduced cellulose crystallinity, and a relative increase in lignin content, with varying degrees of chemical alteration among the six samples. Samples F1 and F4 were in relatively good conditions, whereas F3 and F6 exhibited the most severe degradation. By integrating multiple analytical techniques, this study provides key insights into the preservation condition of the archaeological wood and offers critical guidance for future conservation and restoration efforts. In particular, it supports the implementation of targeted measures, including disinfection, antibacterial treatment, and structural reinforcement, according to the specific preservation conditions of different parts of the wood.