This study is a multicenter phase III uncontrolled open-label trial to evaluate the efficacy,safety and pharmacokinetics of SCT800 in regular prophylaxis and perioperative treatment in patients (<12 years old) with severe hemophilia A who have been previously treated with coagulation factor VIII(FVIII) . This study includes two phases: the screening period and prophylaxis period.Prophylaxis with 25 - 50 IU/kg of SCT800 shall be administered once every other day or three times per week starting from Visit 1 and prophylaxis with SCT800 shall continue for 24 consecutive weeks.

Inclusion Criteria:

• Aged <12 years ;
• Male severe (central laboratory tested FVIII:C <1%) hemophilia A patients;
• Previously received FVIII treatment (prophylactic or bleeding treatment), have the relevant records and are verified to have accumulated EDs ≥150 days（6≤age<12years old）and EDs >50 days（age <6 years old）;
• The bleeding treatment records of at least 3 months before screening can be obtained;
• Negative FVIII inhibitor assay results (laboratory tested Nijmegen-Bethesda assay result <0.6 BU/mL);
• HIV negative; if HIV positive, the viral load <200 particles/uL or <400,000 copies/mL, and HIV patients must satisfy CD4+ count >200/μL;
• The patient or his guardian voluntarily signed the Informed Consent Form.

Exclusion Criteria:

• Known allergy to any coagulation factor VIII or any excipient; known allergy to bovine, rodent or hamster bovine;
• Has a history or family history of blood coagulation factor VIII inhibitor;
• Platelet count <100 × 109/L;
• Clinical liver function test ((glutamic-pyruvic transaminase, glutamic-pyruvic transaminase) ≥ five times the upper limit of normal (ULN) or clinical kidney function test （creatinine) ≥ two times the ULN;
• International normalized ratio (INR) >1.5;
• Patients with other coagulation dysfunction diseases in addition to hemophilia A;
• Patients who used any anticoagulant or anti-platelet treatment (including non-steroidal anti-inflammatory drugs [NSAIDs]) within 1 weeks before the first drug administration or who regularly (e.g., daily, every other day) use anticoagulant or anti-platelet treatment within the clinical trial period;
• Patients who used immunomodulator(e.g., immunoglobulin, corticosteroids,alpha-interferon, prednisone [>10 mg/day and >7 days], or comparable drugs, other than anti-retroviral chemotherapy) within two weeks before the first administration of the study drug or during the clinical trial period;
• Administration of any cryoprecipitate, whole blood or plasma within 30 days prior to administration of study drug.
• Patients with other clinically significant diseases, alcoholism, drug abuse, mental disorders or intellectual disabilities;
• Patients with other severe or clinical significant diseases verified by the investigator to be unable to benefit from the clinical study;
• Patients who participated in other clinical studies within one month before the first drug administration (except FVIII trials) and patients who participated in other FVIII clinical trials after signing the Informed Consent Form;

Hemophilia A is a kind of sex chromosome recessive genetic disease and ofter occurs in male.