Background Coagulation abnormalities in COVID-19 patients accompanied with poor prognosis. This study aimed to determine the prevalence and risk factors of thrombotic events on COVID-19 patients. Methods. We systematically reviewed all the studies about thrombotic events on COVID-19 patients in PubMed, Embase, Web of Science, MedRxiv, bioRxiv, from Dec 1, 2019 to July 5, 2020. The weighted mean difference (MD) or odds ratio (OR) or relative risk (RR) with 95 % confidence intervals (CI) for clinical data in COVID-19 patients with or without thrombotic events was calculated. Results 12 articles contained 1083 patients were included for meta-analysis. The prevalence of thrombosis was 22 % (95 % CI 0.08-0.40) in COVID-19 patients and increased to 43 % (95 % CI 0.29-0.65) after admission to the intensive care unit (ICU). Compared with non-thrombotic patients, thrombotic patients had higher levels of D-dimer (MD = 2.79 mu g/ml, 95 % CI 2.27-3.31 mu g/ml), lactate dehydrogenase (LDH) (MD = 112.71 U/L, 95 % CI 62.40-163.02 U/L), and white blood cells (WBC) (MD = 1.14 *10(9)/L, 95 % CI 0.47-1.81*10(9)/L) while decreased lymphocytes (MD= -0.20*10(9)/L, 95 % CI -0.38 - -0.02*10(9)/L). Age, platelet counts, and male sex tended to be risks while diabetes tended to be a protection for thrombosis for COVID-19 patients, although no statistical difference was achieved. Finally, patients with thrombosis were at a higher risk of death (OR = 2.39, 95 % CI 1.36-4.20). Conclusions Prevalence of thrombosis in COVID-19 patients was high, especially in ICU, though pharmacologic thromboembolism prophylaxis was applied. Therefore, higher levels of D-dimer, LDH, WBC, and decreased lymphocytes needed to be paid close attention to in patients with COVID-19.