Previous academic studies have generally attributed the unearthed charcoal from ancient tombs to its moisture-proofing function. However， this paper argues that while charcoal does absorb minimal residual moisture within tomb chambers， its primary purpose was to prevent tree roots from penetrating coffins （"root interception"）. Modern research reveals that charcoal's hygroscopic property—due to its porous structure—makes it effective as a desiccant in sealed environments， similar to food packaging. Yet in the open underground environment of tombs， charcoal paradoxically draws groundwater toward coffins， accelerating decay. To address this， ancient builders employed an ingenious dual-layer system： outer layers of qinggao mud （green paste clay） for moisture resistance， and inner charcoal layers for root interception. This practice reflects a deep cultural belief in ancient China that the desecration of ancestral remains by tree roots was deemed unacceptable.