By studying the ancient medical cases in past dynasties,treatment on thirst from middle energizer often based on the pathogenesis of exuberance of stomach fire and deficiency of stomach yin,but there were few cases that involved the syndrome and treatment of thirst due to deficiency of spleen yin. Based on the deep discussion on the pathogenesis of thirst,combined with the physiological characteristics of spleen,it put forward that the main pathogenesis of thirst due to deficiency of spleen yin were dysfunction of spleen in ascending clear,hyperactivity of fire due to yin deficiency and deficiency of both qi and yin,and the characteristics of disease and the key points of differentiation were expounded in detail,and the main therapy was nourishing spleen yin and promoting fluid production for moistening tongue,which provided new ideas and methods for the clinical diagnosis and treatment of thirst.