1. Aged 18 to 70 years old, inpatients, male or female, 2. Patients with severe COVID-19: confirmed cases shall be in compliance with guideline of Diagnosis and Treatment Plan for COVID-19 (Version 7) or updated versions.Confirmed cases can be defined if suspected cases have characteristic of following pathogeny or serology: 1) Detect nucleic acid of novel coronavirus positive by real-time fluorescence RT-PCR, 2) Have highly homologous to known novel coronavirus by sequencing, 3) Detect sero specific lgM and lgG positive, IgG specific against new coronavirus positive conversion or the titer of IgG is 4 times higher in convalescent period than in acute period, Adult patients with severe COVID-19 shall meet any of the following: 1) Respiratory distress, RR>=30 times / minute, 2) In the resting state, the oxygen saturation is <=93%, 3) For lung radiology, the lesion has obtained more than 50% obvious improvement within 24-48 hours, 4) Arterial blood oxygen partial pressure (PaO2) / oxygen concentration (FiO2) <=300 mmHg (1mm Hg = 0.133 kPa), 3. Subjects and / or legal guardians of the subjects volunteered to participate in the study and voluntarily signed informed consent.

1. Aged 18 to 70 years old, inpatients, male or female, 2. Patients with severe COVID-19: confirmed cases shall be in compliance with guideline of Diagnosis and Treatment Plan for COVID-19 (Version 7) or updated versions.Confirmed cases can be defined if suspected cases have characteristic of following pathogeny or serology: 1) Detect nucleic acid of novel coronavirus positive by real-time fluorescence RT-PCR, 2) Have highly homologous to known novel coronavirus by sequencing, 3) Detect sero specific lgM and lgG positive, IgG specific against new coronavirus positive conversion or the titer of IgG is 4 times higher in convalescent period than in acute period, Adult patients with severe COVID-19 shall meet any of the following: 1) Respiratory distress, RR>=30 times / minute, 2) In the resting state, the oxygen saturation is <=93%, 3) For lung radiology, the lesion has obtained more than 50% obvious improvement within 24-48 hours, 4) Arterial blood oxygen partial pressure (PaO2) / oxygen concentration (FiO2) <=300 mmHg (1mm Hg = 0.133 kPa), 3. Subjects and / or legal guardians of the subjects volunteered to participate in the study and voluntarily signed informed consent.