Introduction:To summarize the experiences of sequential application with noninvasive (NIV) and highflow nasal cannula oxygen (HFNCO) therapy in the treatment for critically ill patient with severe COVID-19. Case Report: In a mixed Intensive Care Unit, a medical university affiliated hospital in Guizhou Province, China, sequential application with NIV and HFNCO was used in the treatment for a COVID-19 patient with severe acute respiratory distress syndrome (ARDS), and the vital signs and laboratory results were dynamically monitored. A female patient with severe COVID-19 and severe acute respiratory failure was completely recovered from the disease by sequential application with NIV mechanical ventilation and HFNCO therapy. Conclusion: From our limited experience of the case report, NIV and HFNCO could cautiously be used in severe patient with ARDS in condition of close and dynamic monitoring.