COVID-19 which emerged in Wuhan, Hubei Province, China, is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It is typically spread via respiratory droplets and during close contact. The main clinical manifestation is lung injury[1, 2]. Most of the patients have a favorable prognosis, but some rapidly progress to severe and critical cases with respiratory distress syndrome, coagulation dysfunction, multiple organ failure, etc.[3, 4]. Therefore, early identification of the severity is very important to the clinical diagnosis of and treatment for COVID-19. Commonly used clinical laboratory coagulation indexes, such as D-dimer (DD), prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), and fibrinogen (Fg), could sensitively reflect the clotting state of the body.