In order to identify the fibre material of the pall imprint excavated from the Peng-state cemetery in Shanxi, biomass spectrometry was applied to determine the amino acid sequences of the residual protein extracted from the soil underneath the imprint. The sequences were searched against a standard protein sequence database. A well-preserved silk pall sample from the Warring States Period was used as a comparative template. The protein extracted is identified as silk fibroin (Bombyx mori). This finding indicates that the extremely degraded pall was made of silk and that the deceased in the Peng-state cemetery enjoyed high social status. In this way, a novel methodology, which is very promising in uncovering the origin of silk, could be initiated.