(1) Aged 18-65 years, (2) Voluntarily participate in this clinical trial and sign off informed consent form , (3) Diagnosed with severe pneumonia of COVID: respiratory distress, RR >30 times / min, resting oxygen saturation of 93% or less, arterial partial pressure of oxygen / oxygen concentration 300mmHg, SARS-CoV-2 nucleic acid test was positive. (4) Chest imaging confirm COVID-19 featured changes in lung.

(1) Aged 18-65 years, (2) Voluntarily participate in this clinical trial and sign off informed consent form , (3) Diagnosed with severe pneumonia of COVID: respiratory distress, RR >30 times / min, resting oxygen saturation of 93% or less, arterial partial pressure of oxygen / oxygen concentration 300mmHg, SARS-CoV-2 nucleic acid test was positive. (4) Chest imaging confirm COVID-19 featured changes in lung.