This paper explored the ancients' understanding of internal mechanism of the “dryness” phenomenon by analyzing the image of the font of the characters “

bing

（冰）”， “

huang

（黄）” and “

che

（坼）”， and hexagrams such as

kan

（坎） and

kun

（坤）. On one hand， water yin collapses and merges due to the extraction of the internal

yang qi

； on the other hand， the necessary external channels to maintain the normal water flow are destroyed， and the condition for smooth distribution is lost. By analyzing the image of the font and rhyme of the character “

xin

（辛）” and the principle of storing and using ice in

The Commentary of Zuo

（《左传》）， this paper tried to provide the theoretical basis at the image level for traditional Chinese medicine （TCM） in treating dryness with acrid. Based on the above understanding， the TCM theories related to the attributes and functions of

yang qi

and water metabolism of the human body in the

Inner Canon of Yellow Emperor

（《黄帝内经》）， as well as the prescriptions and explanations to treat dryness with acrid in

Treatise on Cold Damage and Miscellaneous Diseases

（《伤寒杂病论》） are explored.