Our study aimed to systematically analyse the risk factors of coronavirus disease 2019 (COVID-19) patients with severe disease. An electronic search in eight databases to identify studies describing severe or critically ill COVID-19 patients from 1 January 2020 to 3 April 2020. In the end, we meta-analysed 40 studies involving 5872 COVID-19 patients. The average age was higher in severe COVID-19 patients (weighted mean difference; WMD = 10.69, 95%CI 7.83-13.54). Patients with severe disease showed significantly lower platelet count (WMD = -18.63, 95%CI -30.86 to -6.40) and lymphocyte count (WMD = -0.35, 95%CI -0.41 to -0.30) but higher C-reactive protein (CRP; WMD = 42.7, 95%CI 31.12-54.28), lactate dehydrogenase (LDH; WMD = 137.4, 95%CI 105.5-169.3), white blood cell countWBC), procalcitoninPCT, D-dimer, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and creatinineCr. Similarly, patients who died showed significantly higher WBC, D-dimer, ALT, AST and Cr but similar platelet count and LDH as patients who survived. These results indicate that older age, low platelet count, lymphopenia, elevated levels of LDH, ALT, AST, PCT, Cr and D-dimer are associated with severity of COVID-19 and thus could be used as early identification or even prediction of disease progression.