• Voluntarily participate in the study and signed informed consent with good compliance;

• Age: 18 or above (when signing the informed consent form); Eastern Cooperative Oncology Group (ECOG) performance status (PS) score of 0 to 2; Life expectancy ≥ 24 weeks;

• Patients diagnosed with Primary myelofibrosis (PMF), post polycythemia vera myelofibrosis (post-PV-MF), or post essential thrombocythemia myelofibrosis (post-ET-MF);

• Those with moderate or high risk myelofibrosis evaluated according to Dynamic International Prognostic Scoring System (DIPSS) prognostic grading criteria, or those with high risk myelofibrosis according to National Comprehensive Cancer Network (NCCN) guidelines prognostic grading criteria;

• Patients with poor efficacy of JAK inhibitors (for monotherapy of TQB3909, phase Ib and phase II cohort 2);

• Patients who had not received JAK inhibitor treatment (for phase Ib and phase II cohort 2)

• Spleen enlargement;

• Peripheral blood primary cells and bone marrow primary cells are ≤10%;

• No growth factor, colony stimulating factor, thrombopoietin or platelet transfusion was received within 2 weeks before the examination, and the blood routine indexes met the requirements within 7 days before the first administration

• The Main organ function is normal;

• Men and women of childbearing age should agree to use contraceptive measures during the study period and within 6 months after the end of the study.