The pathogenesis of pulmonary interstitial fibrosis is complex.Recent studies have demonstrated that imbalance of Th1/Th2 cytokines, remodeling of extracellular matrix, activation and proliferation of fibroblasts, blood coagulation mechanism, local inflammatory infiltration and alveolar epithelial injury play an important role in its onset.This paper explores the role of abnormal changes in the mechanism of coagulation-fibrinolysis during the onset of pulmonary interstitial fibrosis from the perspective of coagulation mechanism in vivo, and puts forward a modern concept of syndrome differentiation in traditional Chinese medicine(TCM), “lung deficiency and collateral stasis”.“Tonifying deficiency and dredging collateral” is the principle of treatment in pulmonary interstitial fibrosis, providing a new theoretical basis and therapy for the treatment of pulmonary interstitial fibrosis under the guidance of TCM theory.