The Nanhai Ⅰ Shipwreck is China's first ancient shipwreck to be salvaged from the ocean. It is renowned for its well-preserved condition, large size, and abundant cultural relics. The wood of the Nanhai Ⅰ Shipwreck contains a considerable amount of iron sulfides, which threaten the shipwreck's long-term and safe preservation. However, a significant gap exists in studying the iron sulfides in the shipwreck's wood. This study selected three typical cabins of the Nanhai Ⅰ shipwreck (No. 4, No. 7, and No. 11), which had significant differences in the quantities of iron cargo loaded, as the research subjects. Wet chemistry methods, optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and inductively coupled plasma emission spectrometer (ICP) were used to analyze the wood degradation of different cabins, as well as the distribution, morphology, and composition of the iron sulfides, and sulfur and iron content. The results showed that the degree of wood degradation varied among different cabins. The ratio of holocellulose content to lignin content (H/L) of the wood in cabins No.4 and No.7 was relatively low, indicating a higher degree of degradation. In contrast, the H/L value of the wood in cabin No.11 was the highest, indicating the lowest degree of degradation. The inorganic sediments in the wood of the Nanhai Ⅰ shipwreck are primarily iron sulfides, mainly including pyrite (FeS₂), hydroxylated iron oxide (FeOOH), and siderite (FeCO₃). These compounds are distributed within the wood cell structures such as tracheids and wood rays, and are attached to the inner layer of cell walls. Due to the ironware's loading conditions and the wood's preservation state, the iron content in the wood of the Nanhai Ⅰ shipwreck is relatively high and varies significantly among different cabins. The iron content in the wood of cabin No. 11 is mainly below 2.5%, while in cabins No.4 and No.7, it is mainly between 1%~5% and between 0.3%~30%, respectively. The sulfur element primarily originates from the degradation reaction of marine microorganisms and diffuses into the wood as hydrogen sulfide gas. Then it reacts with lignin to produce mercaptan and accumulates in the wood. Consequently, the sulfur content is relatively low, and the differences between cabins are minor, mainly concentrated between 5% and 10%. Based on this study, the degradation of wood and the distribution and content of iron sulfides in the wood of different cabins of the Nanhai Ⅰ shipwreck were investigated. The findings can guide the removal of iron sulfides from the wood of the Nanhai Ⅰ shipwreck.