Patients with severe ITP will be randomly assigned to three groups: rhTPO group, Herombopag Group, Herombopag combined with rhTPO group. The effective rate of treatment, the rate and amplitude of platelet increase, the response time of platelet maintenance, and the effect of combination therapy on hemostasis will be compared. At the same time, the investigators will analyze the markers of thrombosis and thrombotic events to assess the safety of combination therapy.