Previous studies have focused primarily on inorganic artifacts such as bronze vessels, but given less attention to organic ones. This is due to the susceptibility of organic materials to decay and degradation, often resulting in their complete disappearance or survival only in forms of remnants. The plant weavings unearthed from tombs are organic artifacts, typically found in extremely poor conditions. Identification of their materials through organic residue analysis forms a basis for their subsequent preservation and the better understanding of their value. This study focused on the woven mat-like material attached to a bronze Gui from Tomb M1020 at the Beibai’e Cemetery, using three methods—fiber microscopic observation, phytolith analysis, and liquid chromatography-mass spectrometry (LC-MS)—for analysis. Plant fibers could be observed in certain areas of the mat. These fibers were generally short, slender, and exhibited some curvature, often appearing alongside epidermal cells. The observed epidermal cells were elongated and serrated on both sides, with the serrations typically being semi-elliptical in shape, tapering slightly at the top compared to the base. The undispersed epidermal cells were often connected to form a continuous layer, with the serrations interlocking like a zipper. The results of the fiber microscopic observation were consistent with the characteristics of Gramineae plants, particularly reeds. Notably, around the undispersed epidermal cells, fragments of the “reed membrane” with stomata and traces of epidermal cell arrangement were observed. The “reed membrane” was a key marker for identifying reeds. In addition, a statistical analysis of 200 phytoliths was conducted. Among the identifiable ones, over 70% were epidermal phytoliths from Gramineae, with a small number of saddle-shaped phytoliths (from Gramineae) and spinulose phytoliths also present. Among common weaving materials, two types belong to the Gramineae family: bamboo and reed. Referring to previous studies on the microscopic features of ancient reed mats as well as modern reed and bamboo, it is evident that the morphological characteristics and arrangement of the aforementioned phytoliths were consistent with those of reed stem phytoliths, but did not match the microscopic morphology of bamboo stems. The mat-like weaving unearthed from the archaeological site has undergone significant degradation of its organic components due to prolonged burial, resulting in substantial changes in the types and quantities of these components. However, it is still possible for species-specific metabolic small molecules to remain. This study utilized LC-MS to study the mat-like weaving unearthed from Tomb M1020 at the Beibai’e Cemetery, along with reagent blank controls. Compared to the total ion chromatogram of the blank controls, that of the archaeological samples had a few characteristic peaks identified, leading to the identification of 14 small molecules by searching natural product databases. Among them, gomisin O, pterosin B, and methylparaben are plant-derived metabolites, and choline, sphingosine, and phytosphingosine may be of the plant origin. These findings indicate the plant-derived nature of the archaeological samples. This study focused on the mat-like weaving attached to a bronze Gui from Tomb M1020 at the Beibai’e Cemetery. Using fiber microscopic observation and phytolith analysis, it was determined that its biological origin was reed. The plant origin was further verified through LC-MS. Additionally, by correlating the findings with historical texts and the actual conditions at the archaeological excavation site, it was inferred that the archaeological sample was a reed mat, placed between the outer coffin lid and the inner coffin lid for use as a “dust mat”. Furthermore, a large number of mat-like remnants were also found beneath the bottom board of the coffin, where they were well preserved due to their proximity to the original soil. Comparing these remnants with the scientifically analyzed archaeological samples indicates that they were also reed mats, positioned beneath the tomb owner as a “resting mat”. A large number of mat-like weaving remnants were found in Tomb M1020 at the Beibai’e Cemetery, and similar situations are also common in other tombs from the early Spring and Autumn Period. This indicates that the burial mat played an important role throughout the burial process and that the practice of using burial mats was well established during this period.  The research findings provide physical evidence of burial mats used during the early Spring and Autumn Period, contributing to a better understanding of the funerary practices of that time. In addition, they offer an entry point for reconstructing the social landscape following the Eastern Migration of the Zhou Dynasty.