Background: Since December 2019, an outbreak of Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) initially emerged in Wuhan, China, and has spread worldwide now. Clinical features of patients with COVID-19 have been described. However, risk factors leading to in-hospital deterioration and poor prognosis in COVID-19 patients with severe disease have not been well identified. Methods: In this retrospective, single-center cohort study, 1190 adult inpatients (≥ 18 years old) with laboratoryconfirmed COVID-19 and determined outcomes (discharged or died) were included from Wuhan Infectious Disease Hospital from December 29, 2019 to February 28, 2020. The final follow-up date was March 2, 2020. Clinical data including characteristics, laboratory and imaging information as well as treatments were extracted from electronic medical records and compared. A multivariable logistic regression model was used to explore the potential predictors associated with in-hospital deterioration and death. Results: 1190 patients with confirmed COVID-19 were included. Their median age was 57 years (interquartile range 47-67 years). Two hundred and sixty-one patients (22%) developed a severe illness after admission. Multivariable logistic regression demonstrated that higher SOFA score (OR 1.32, 95% CI 1.22-1.43, per score increase, p < 0.001 for deterioration and OR 1.30, 95% CI 1.11-1.53, per score increase, p = 0.001 for death), lymphocytopenia (OR 1.81, 95% CI 1.13-2.89 p = 0.013 for deterioration; OR 4.44, 95% CI 1.26-15.87, p = 0.021 for death) on admission were independent risk factors for in-hospital deterioration from not severe to severe disease and for death in severe patients. On admission D-dimer greater than 1 μg/L (OR 3.28, 95% CI 1.19-9.04, p = 0.021), leukocytopenia (OR 5.10, 95% CI 1.25-20.78), thrombocytopenia (OR 8.37, 95% CI 2.04-34.44) and history of diabetes (OR 11.16, 95% CI 1.87-66.57, p = 0.008) were also associated with higher risks of in-hospital death in severe COVID-19 patients. Shorter time interval from illness onset to non-invasive mechanical ventilation in the survivors with severe disease was observed compared with non-survivors (10.5 days, IQR 9.25-11.0 vs. 16.0 days, IQR 11.0-19.0 days, p = 0.030). Treatment with glucocorticoids increased the risk of progression from not severe to severe disease (OR 3.79, 95% CI 2.39-6.01, p < 0.001). Administration of antiviral drugs especially oseltamivir or ganciclovir is associated with a decreased risk of death in severe patients (OR 0.17, 95% CI 0.05-0.64, p < 0.001).