Based on the theory ofYe Tianshi that“disease progressively, chronic diseases transforming to collaterals”, physiological and pathological features of the lung were combined to elucidate the pathogenesis of pulmonary fibrosis, which had the characteristics of disease progressed from superficial location to deeper regions, and the disease transformed from functional to organic disease lesions. The initial stage was mainlyqi disorders and dysfunction due to evilqi invasion andqi disorder in the lung collaterals. The treatment was to disperseqi and regulate collaterals. In the middle or later stage, the main pathogenesis was lung deficiency and blood stasis due to the obstruction of lung collaterals, as well as long-term mixture of deficiency and stasis. The treatment was to remove obstruction and tonify deficiency. Therefore, dispersingqi and regulating collaterals, as well as removing obstruction and tonifying deficiency were the main treatment methods of pulmonary fibrosis. Analysis on pulmonary fibrosis from the theory of“disease progressively, chronic diseases transforming to collaterals”, can give a good summary and explanation of the disease occurrence, progress and development with important clinical significance.