The coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 was identified in December 2019.The symptoms include fever,cough,dyspnea,early symptom of sputum,and acute respiratory distress syndrome (ARDS).Mesenchymal stem cell (MSC) therapy is the immediate treatment used for patients with severe cases of COVID-19.Herein,we describe two confirmed cases of COVID-19 in Wuhan to explore the role of MSC in the treatment of COVID-19.MSC transplantation increases the immune indicators (including CD4 and lymphocytes)and decreases the inflammation indicators (interleukin-6 and C-reactive protein).High-flow nasal cannula can be used as an initial support strategy for patients with ARDS.With MSC transplantation,the fraction of inspired O2 (FiO2) of the two patients gradually decreased while the oxygen saturation (SaO2) and partial pressure of oxygen (PO2) improved.Additionally,the patients’ chest computed tomography showed that bilateral lung exudate lesions were adsorbed after MSC infusion.Results indicated that MSC transplantation provides clinical data on the treatment of COVID-19 and may serve as an altative method for treating COVID-19,particularly in patients with ARDS.