Experimental: avatrombopag

Avatrombopag 20 mg/d will be taken orally from +D7 after haplo-HSCT until reaching the adjustment indication or to +D60 after haplo-HSCT. Routine treatment is allowed.~Adjustment indication:~When PLT\<50×10\^9/L or PLT transfusion dependent on the +D30 after haplo-HSCT, increase the dosage to 40 mg/d; When the dosage has been increased to 40 mg/d, and PLT≥80×10\^9/L excluding the factor of PLT transfusion, decrease the dosage to 20 mg/d; When PLT≥80×10\^9/L for 7 consecutive days excluding the factor of PLT transfusion, or PLT≥300×10\^9/L excluding the factor of PLT transfusion, stop administration; When PLT\<50×10\^9/L or become PLT transfusion dependent after stopping administration, initiate administration again at the dosage 40 mg/d.~PLT transfusion Indication: When PLT\<20×10\^9/L, and/or with the symptom or risk of bleeding.

Placebo_comparator: Placebo

Placebo 20 mg/d will be taken orally from +D7 after haplo-HSCT until reaching the adjustment indication or to +D60 after haplo-HSCT. Routine treatment is allowed.~Adjustment indication:~When PLT\<50×10\^9/L or PLT transfusion dependent on the +D30 after haplo-HSCT, increase the dosage to 40 mg/d; When the dosage has been increased to 40 mg/d, and PLT≥80×10\^9/L excluding the factor of PLT transfusion, decrease the dosage to 20 mg/d; When PLT≥80×10\^9/L for 7 consecutive days excluding the factor of PLT transfusion, or PLT≥300×10\^9/L excluding the factor of PLT transfusion, stop administration; When PLT\<50×10\^9/L or become PLT transfusion dependent after stopping administration, initiate administration again at the dosage 40 mg/d.~PLT transfusion Indication: When PLT\<20×10\^9/L, and/or with the symptom or risk of bleeding.