Inclusion Criteria:

- Clinical diagnosis of COVID-19 pneumonia；

- 3 to 8 weeks after the onset of the first symptoms of COVID-19 infection;

- Modified Medical Research Council (mMRC) score ⩾2 or hypoxemia;

- Imaging severity assessment of pneumonia: CT severity scores (CTSS):≥5；

- Signed the informed consent.

Exclusion Criteria:

- Participants still admitted to intensive care unit at the time of enrollment;

- Known prior structural lung disease, including pulmonary fibrosis, severe COPD,
severe bronchiectasis, and lung destruction;

- Taking glucocorticoids or immunosuppressants because of other chronic diseases;

- Contraindications of glucocorticoid;

- Heart failure(NYHA III or IV);

- Participants with renal replacement therapy;

- Psychiatric disorders or cognitive impairments;

- The expected survival time is less than six months due to diseases other than
COVID-19 pneumonia.