Weathering is commonly observed in stone cultural relics around the world. Superficial weathering in forms of granular disaggregation, powdering and flaking on the stone surface is one of the most serious damages to the stone relics, since the surface carries most of artistic, historical information. Apparently, the determination on the thickness of superficially weathered layer of stone cultural relics is critical to their conservation. However, the methodology for quantitative analyses of the thickness of superficial weathered layer on stone relics remains very limited. In this study, we carefully study the moisture absorption and pore structure evolution of stone relics with respect to its weathering. We find out that the thickness of superficial weathered layer can be derived from the moisture absorption or pore structure information. Data acquired from these methods are consistent with each other and in well agreement with the results obtained by currently using techniques such as drilling resistance measurement etc.