In order to understand the relationship between the composition of leather and its tanning technology, an investigation and classification of leather artifacts collected in museums within Inner Mongolia was carried out. Investigation by modern analytical technology, including scanning electron microscopy (SEM) and X-ray diffraction (XRD) was applied to further analyze the relationship between leather composition and leather’s physical and chemical properties. The results show that the composition of the leather artifacts correlates with the tanning technology. The leather tanned by old methods has more CC14 extractable but less ash than the leather tanned by modern methods, while the leather tanned by modern technology contains chromium, which is characteristic of modern tanning methods. Both old and new samples have NaCl, which was used as a preservative.