Inclusion Criteria:
* Age above 18 years.
* Male and female
* Must understand and voluntarily sign an Informed Consent for study participation obtained prior to undergoing any study-specific procedures
* Diagnosed as COVID-19 based upon SARS-CoV-2 RT-PCR test positive
* Clinical diagnosis meets severe and/or critical parameters
* Male participants must be willing to ensure their partners do not become pregnant either by practicing abstinence or the use of condoms during sexual activity
Exclusion Criteria:
* Participation in another clinical study (with use of another Investigational Medical Product) within 3 months prior to study treatment start
* Unwillingness or inability to comply with study procedures
* Patients with serious basic diseases that affect survival, including blood diseases, cachexia, active bleeding, severe malnutrition, etc.
* Clinically active malignant disease
* Subjects who are receiving ECMO and CRRT currently
* History of known pulmonary embolism or known secondary anti-phospholipid syndrome
* Known or suspected hypersensitivity to any components used to culture the AdMSCs, e.g. BSA and sulfur containing products (e.g., DMSO)
* Known or suspected allergic to diphenhydramine.
* Major trauma or surgery within 14 days of study treatment start
* Mental condition rendering the subject (or the subject's legally acceptable representative\[s\]) unable to understand the nature, scope and possible consequences of the study
* Alcohol, drug, or medication abuse within one year prior to study treatment start
* Any condition that, in the Investigator's opinion, is likely to interfere with evaluation of the AdMSC therapy or satisfactory conduct of the study
* Irreversible severe end organ failure, such as heart failure/attack, stroke, liver and renal failure due to other disease conditions
* Patients or family history with hypercoagulable status, such as protein C/protein S deficiency, factor V Leiden, prothrombin gene mutation, dysfibrinogenemia, etc.
* History of long-term use of immunosuppressive agents
* Organ transplants in the past 6 months
* Pregnant, breastfeeding, or desire to become pregnant or unwilling to practice birth control during participation in the study duration, unless surgically sterilized or postmenopausal during the study.
* Patients with previous pulmonary obstructive pneumonia, severe pulmonary interstitial fibrosis, alveolar proteinosis, allergic alveolitis, and other known viral pneumonia or bacterial pneumonia before COVID-19 infection. The pulmonary imaging revealed the interstitial damage of lungs before the COVID-19 confirmed.
* QT interval shows greater than 450 ms in males and 470 ms in females in the medical histories or during screen EKG test.
* Subjects are not medically unstable at time of infusion including but not limiting unstable hypertension, pulse, oximetry, etc.
