1. Participation in the study is not in accordance with the rights and interests of the patient based on PIs judgement, or any other circumstances that investigators consider inappropriate for participation, 2. With bleeding or bleeding associated with severe coagulation disorders (except for disseminated intravascular coagulation unrelated to heparin therapy), with a history of severe type II heparin-induced thrombocytopenia, whether or not caused by unfractionated heparin or low-molecular-weight heparin (significantly reduced by platelet count previously), active peptic ulcer or organ damage with bleeding tendency, clinically significant active bleeding , cerebral hemorrhage, 3. Have any situation that treatment with low molecular heparin is required, 4. Females who are pregnant or likely to be pregnant, or who are lactating and unable to stop breastfeeding, or who have positive pregnancy tests during screening, 5. Males or females who have a birth plan or are unwilling to take reliable contraceptive measures for contraception within 90 days from signing the informed consent to the last dose, 6. With severe liver disease: patient with basic diseases of liver cirrhosis , or alanine aminotransferase (ALT) / aspartate aminotransferase (AST) increased more than 5 times of the normal upper limit, 7. Patients known to have severe renal impairment [creatinine clearance (CcCl) < 30 ml / min], or to receive continuous renal replacement therapy, hemodialysis or peritoneal dialysis, 8. At rest without oxygen inhalation, SPO2 <=93%, or PaO2/ FiO2 <=300 mmHg, 9. Patients allergic to enoxaparin, heparin or its derivatives, including other low-molecular-weight heparins.

1. Participation in the study is not in accordance with the rights and interests of the patient based on PIs judgement, or any other circumstances that investigators consider inappropriate for participation, 2. With bleeding or bleeding associated with severe coagulation disorders (except for disseminated intravascular coagulation unrelated to heparin therapy), with a history of severe type II heparin-induced thrombocytopenia, whether or not caused by unfractionated heparin or low-molecular-weight heparin (significantly reduced by platelet count previously), active peptic ulcer or organ damage with bleeding tendency, clinically significant active bleeding , cerebral hemorrhage, 3. Have any situation that treatment with low molecular heparin is required, 4. Females who are pregnant or likely to be pregnant, or who are lactating and unable to stop breastfeeding, or who have positive pregnancy tests during screening, 5. Males or females who have a birth plan or are unwilling to take reliable contraceptive measures for contraception within 90 days from signing the informed consent to the last dose, 6. With severe liver disease: patient with basic diseases of liver cirrhosis , or alanine aminotransferase (ALT) / aspartate aminotransferase (AST) increased more than 5 times of the normal upper limit, 7. Patients known to have severe renal impairment [creatinine clearance (CcCl) < 30 ml / min], or to receive continuous renal replacement therapy, hemodialysis or peritoneal dialysis, 8. At rest without oxygen inhalation, SPO2 <=93%, or PaO2/ FiO2 <=300 mmHg, 9. Patients allergic to enoxaparin, heparin or its derivatives, including other low-molecular-weight heparins.