Idiopathic pulmonary fibrosis （IPF） can be classified as pulmonary collateral disease，and its pathogenesis is mainly characterized by the loss of Qi meridian nourishment，the loss of Yin meridian nourishment，and the formation of blood stasis in the blood vessels. Qi Yin deficiency is the pathological basis that runs through IPF，and obstruction of meridians and collaterals is a key element in the development of the disease. The dysfunction of "spleen being in charge of the defensive function" is closely related to the formation of the pathological pattern of "lung deficiency and collateral stasis" in IPF. The term "spleen being in charge of the defensive function" originated from the Yellow Emperor's Inner Canon. If the spleen is healthy，the Qi will be filled with vitality. Positive energy is stored inside，evil cannot be dried up. Its concept is quite similar to the immune defense function in modern medicine. If the principle of "spleen being in charge of the defensive function" is lost，the key structure and function of the IPF alveolar epithelial barrier may be abnormal，and it can interact with various innate immune cells to promote inflammation and fibrosis processes. Therefore，this article explains the imbalance of immune homeostasis in IPF alveolar epithelium from two aspects：the barrier function of alveolar epithelial cells（AECs） and their interaction with innate immune cells. And based on the theory of "spleen being in charge of the defensive function"，using traditional Chinese medicine for strengthening the spleen and nourishing Qi to treat IPF from the perspective of the spleen. This not only strengthens the scientific connotation of "spleen being in charge of the defensive function" in the pathogenesis of IPF，but also provides new research directions and ideas for its future clinical prevention and treatment.

spleen being in charge of the defensive function;lung deficiency and collateral stasis;idiopathic pulmonary fibrosis;epithelial homeostasis;alveolar epithelial cells