Up to 350 words. NoTreatment of COVID-19 pneumonia has been a difficult problem. Improving patient immunity and reducing lung injury induced by COVID -19 is of great significance. Our small sample clinical study (6 patient) showed that nebulization mesenchymal stem cells (MSCs) exosomes is a new method to treat COVID-19 pneumonia. Nebulization MSCs exosomes did not induce acute allergic reaction and no secondary allergic reaction. It can reduce the levels of C-reactive protein in plasma, promote the absorption of pulmonary lesions, and reduced the time of hospitalization for COVID-19 pneumonia patients. Nebulization MSCs exosomes is a safe, effective and simple method. Using nebulization MSCs exosomes from the beginning of the treatment may benefit patients more. references allowed. Abstracts may be submitted at a later date.