Abstract ： Pulmonary fibrosis is one of the important complications of corona virus disease 2019 (COVID-19)，which greatly affects the survival rate and quality of life of patients. The authors sorted out and analyzed the etiology，pathogenesis，symptoms and signs，and clinical treatment of COVID- 19 and pulmonary fibrosis caused by COVID- 19， and believed that turbidity toxin is the key cause of both. Innovative evolution laws of pathogenesis of pulmonary fibrosis caused by COVID- 19 were proposed as follows： in the early stage， internal retention of turbidity toxin and the qi movement is blocked； in the middle- late stage， there are phlegm coagulation and blood stasis， and the toxin damages the lung collateral；in the recovery stage，there are damage to yin，qi consumption，deficiency of healthy qi，and lingering pathogen. Clinical treatment should nip the disease in the bud；it should not only pay attention to removing turbidity and toxin and dispelling phlegm and blood stasis，but also pay attention to boosting qi and nourishing yin， so as to achieve the effect of preventing and treating pulmonary fibrosis caused by COVID-19 and improving the quality of life of patients.