Abstract: The theory of “muddy between host and guest” was proposed by Xue Shengbai to characterize the pathogenesis of dampness-heat pathogens penetrating the nutrient-blood phase and intermingling with blood vessels. The “inflammation-cancer transformation” of chronic gastritis is a complex process evolving from non-resolving inflammation to gastric cancer, and its pathogenetic evolution aligns with the features of “muddy between host and guest”, that is, deficient healthy qi with stubborn entrenchment of pathogenic factors. Spleen-stomach deficiency constitutes the root cause, with internal retention of dampness-heat. Dampness obstructs qi movement and heat scorches to generate stasis; these three factors intermingle inseparably, accumulate and transform, ultimately forming the state of “muddy between host and guest”. Prolonged retention of pathogenic factors covertly consumes healthy qi, leading to repeated gastric mucosal injury and aberrant repair, which gradually progresses to atrophy, intestinal metaplasia, dysplasia, and even carcinogenesis. Treatment adheres to the general principle of “separating host and guest”, dynamically capturing the pathogenetic evolution, and flexibly applying the method of supporting healthy qi and eliminating pathogens. Through measures such as strengthening the spleen and consolidating the root, clearing heat and resolving dampness, and resolving stasis and unblocking collaterals, the entangled state of dampness, heat, and stasis is resolved. The aim is to halt disease progression and reverse precancerous lesions, thereby providing a theoretical basis and clinical rationale for the prevention and treatment of this disease with traditional Chinese medicine.