Objective：To investigate the clinical characteristics，treatment and prognosis of coronavirus disease 2019（COVID-19）. Methods：Totally of 51 patients with severe and critical COVID-19 in Chongqing Three Gorges Center Hospital from January 21，2020 to February 25，2020 were included. Cases were analyzed retrospectively for demographic，clinical manifestations，laboratory in－dexes，imaging data，comorbidity，treatment and prognosis. Results：Patients were divided into severe group（n=35，68.6%） and critical group（n=16，31.4%） according to the guideline for diagnosis and treatment of novel coronavirus infected pneumonia. The most com－mon symptoms at onset of illness were fever，cough，expectoration，dyspnea and fatigue. The rate of respiratory was faster in critical group than in severe group（P=0.027）. The ratio of neutrophils was significantly higher in critical group than in severe group（P=0.012）. The serum levels of lactate dehydrogenase was significantly higher in critical group than in severe group（P=0.028）. The serum D-dimer levels were significantly higher in critical group than in severe group（P=0.013）. The serum procalcitonin concentration was significantly higher in critical group than in severe group（P=0.013）. The serum levels of albumin was significantly lower in critical group than in severe group（P=0.004）. The oxygenation index（PO2/FiO2） was lower in critical group than in severe group（P=0.040）. The percentage of complications such as acute respiratory distress syndrome（ARDS），acute respiratory failure，sepsis，shock and acute heart failure occoured in critical group were higher than in severe group（P=0.006，0.000，0.004，0.012，0.027，respectively）. The per－centage of treatment such as ribavirin，hemofiltration，noninvasive mechanical ventilation，invasive mechanical ventilation and prone position ventilation accepted were higher in the critical group than in the severe group（P=0.008，0.012，0.001，0.000，0.027，respec－tively）. The 51 COVID-19 patients，24 cases（47.1%） were cured and discharged，17 cases（33.3%） were hospitalized，6 cases（11.8%） were transferred to the mild pneumonia area due to the improvement of their condition，and 4 cases（7.8%） died. Conclusion：Elderly patients and those with chronic medical illness may be more likely to develop into severe and critical COVID-19. The laboratory indexes are more abnormal in critical group than those in severe group. The critical COVID-19 patients are more likely have ARDS than se－vere COVID-19. The mortality of critical COVID-19 is higher than that of severe COVID-19.