In November 1981,an ancient female cadaver of Qidan nationality in wulanchatu League of InnerMongolia was excavated.This cadaver was estimated approximately 25 year of age.She has been buriedfor about 900 years.The cadaver was a mummified corpse,and preserved in a comparatively intact state. The hair was intact and dark brown in colour.All viseral organs were dreg-like and dark brown incolour.The individual organ could not be identified from its exernal appearance.Only lungs werepreserved,adhering to the back of the thoracic cavity and looked like dry leaves.The peritonem wasdry and translucent and contained a few blood vessels.The muscles were also dry and dark brown or brownishgray in colour.The alveoli and the parenchma of the lung as well as bacterial spores were identified.The histologicalstructure of tissues from the heart region looked like the cross section of cardiac fiber.Collagenous fiberswere seen.Other tissues were mostly autolyzed.The cadaver were group B.According to results of toxic analysis,larger amount of arsenic was demonstratedin tissues from the stomach region.So it was deduced that the lady might die of an arsenical poisoning.Factors involving in the well preservation of this case are discussed.