The Han Dynasty stone coffin unearthed from M23 tomb in Jintang Lijialiangzi of Chengdu has suffered from surface weathering phenomena such as powdering, peeling and other diseases and hence needs protection and restoration as soon as possible. On-the-spot investigation shows that the main weathering diseases of the stone artifact include cracks, sheets, granules, powders, etc. In this paper, the authors used X-ray diffraction (XRD), polarized light microscopy, and scanning electron microscopy (SEM) to analyze the microstructure and structure of Jintang stone artifact. The results show that the stone artifact is made of red sandstone, and the main detrital minerals are quartz, albite, rock debris and a small amount of mica. The main cement is calcium with a small amount of carbonaceous and argillaceous material. It is also shown that the main factors responsible for the sandstone weathering is the dissolution loss of calcareous cement and the disintegration of muddy cement with water, together with the influence of the weathering alteration of debris and feldspar debris. The results obtained by the authors will help to provide basic scientific data for the post-protection and restoration of this stone coffin.