Abstract： This study systematically traces the theoretical origins and historical context of YE Tianshi's stomach yin theory through the developmental framework of Chinese medicine spleen-stomach theory. In response to the clinical challenges posed by the prevalence of warm diseases and frequent depletion of stomach yin during the Qing Dynasty， YE proposed the core concept that "the stomach favors moisture". He emphasized the physiological characteristics of the stomach as "yang-earth preferring cool-moisture"，advocated for the separate management of the spleen and stomach， and developed innovative methods for nourishing stomach yin， including sweet-cool moistening and sour-sweet combination for nourishing yin. These contributions addressed the limitations of LI Dongyuan's spleen-stomach theory， which overemphasized warm-tonifying and yang-raising methods. The article elaborates on the etiology，pathogenesis， and differentiation principle of stomach yin deficiency syndrome （e.g.，hunger without desire to eat，epigastric burning pain，red tongue with scant coating）. Through case analyses from Lin Zheng Zhi Nan Yi An（ Case Records as a Guide to Clinical Practice），it demonstrates YE's clinical expertise in flexibly applying therapeutic strategies such as the method of clearing heat to nourish stomach and the method of sweet-moderation benefiting stomach.