Based on the theory of "mutual interference of clear and turbid Qi" in Huangdi Neijing（《黄帝内经》）， this study explored the pathogenesis of spleen and stomach diseases and the therapeutic effects of Banxia Xiexintang on them. It suggested that "mutual interference of clear and turbid Qi" represents a pathological state of Yin and Yang disturbance and imbalance in Qi circulation due to the mixture of clear and turbid Qi， which can elucidate the pathogenesis of spleen and stomach diseases. According to this theory， the pathogenesis of spleen and stomach diseases was summarized as Qi disorder in spleen and stomach， disharmony between Ying Qi and Wei Qi， and conflict between cold and heat. Banxia Xiexintang， as a crucial prescription for treating spleen and stomach diseases， achieves its therapeutic effects by dispersing stagnation with pungent flavor， descending adverse Qi with bitterness， regulating Ying Qi and Wei Qi， and harmonizing cold and heat. By regulating Qi circulation， balancing internal and external factors， and addressing deficiency and excess， it can rectify the pathological state of "mutual interference of clear and turbid Qi" of spleen and stomach diseases. Modern research reveals that Banxia Xiexintang can modulate gastrointestinal motility， restore mucosal immune barrier function of the digestive system， and exhibit optimal therapeutic effects when combined with both cold-cool and warm-hot medicines， aligning with its therapeutic role under the theory of "mutual interference of clear and turbid Qi". By delving into the essence of the "mutual interference of clear and turbid Qi" theory and exploring the pathogenesis of spleen and stomach diseases and the therapeutic effects of Banxia Xiexintang based on this theory， this study further elucidated the inherent connection between spleen and stomach diseases and the "mutual interference of clear and turbid Qi" theory， offering insights and theoretical references for the clinical diagnosis and treatment of spleen and stomach diseases.