Objective To investigate the clinical characteristics of severe coronavirus disease 2019 (COVID-19) and explore the relevant risk factors that affect outcomes of the patients. Methods A retrospective analysis was performed on the data of the patients with severe COVID-19 admitted to the ICU of Huoshenshan Hospital of Wuhan City during the period from February to April, 2019. The patients were classified into survival group and death group. The general data, clinical manifestations, laboratory examinations, and treatments were compared between the 2 groups. Results A total of 122 severe COVID-19 patients were included in the study, 56 died and the fatality rate was 45.9%. The proportion of comorbidities of coronary heart disease in death group was significantly higher than that in the survival group [19.6%(11/56) vs. 7.6%(5/66), P=0.049]. Compared with patients in the survival group, the platelet count in the death group decreased [190.1(132.3, 245.0)×10⁹/L vs. 217.0(176.0,262.3)×10⁹/L, P=0.015] and the levels of C-reactive protein and brain natriuretic peptide in the death group increased [37.4(4.3,125.6) mg/L vs. 8.9(2.7, 51.4) mg/L, P=0.027 and 65.17(18.84, 167.71) pg/ml vs. 16.60(0.01, 67.68) pg/ml, P=0.007]. The prothrombin time and thrombin time in the death group were longer than those in the survival group [14.20(13.22, 15.86) s vs.13.27(12.16, 14.27) s, P<0.01 and 16.32(15.11, 18.02) s vs. 15.75(14.81, 16.62) s, P=0.037]. Dynamic observation data showed that there were significant differences in neutrophil count, lymphocyte count, neutrophil/lymphocyte ratio and levels of both lactate dehydrogenase and α-hydroxybutyrate dehydrogenase (α-HBDH) between the two groups. ROC curve analysis showed that LDH and α-HBDH were of high value in predicting outcome, and the area under the curve was more than 0.7. Conclusions We should pay close attention to the changes of blood routine, LDH, and α-HBDH for older patients with underlying diseases. This will help us to identify the patients with high risk of death in the early stage, and take effective treatment measures as early as possible to improve the prognosis.