Patients who have acute myeloid leukemia and will undergo haplo-identical donor hematopoeitic cell transplantation (haplo HCT) are potential candidates of this trial. Participants will randomized into two arms: Arm A will undergo a typical haplo HCT, while Arm B will receive an coinfusion of an unrelated cord blood unit (haplo-cord HCT) in addition to Arm A. Progression-free survival, overall survival, cumulative incidence of relapse and nonrelapse mortality will be recorded as endpoints.

Inclusion Criteria:

1. Age 18 to 60 years old;
2. Patients with AML;
3. With available minimal residual disease (MRD) parameters assessed by flow cytometry (FCM) and/or quantitative real-time PCR (qPCR)
4. Having no available HLA-matched donor, and willing to undergo haplo-HCT and having a suitable haploidentical donor
5. With Eastern Cooperative Oncology Group (ECOG) performance status of 0-3
6. Signing informed consent form, having the ability to comply with study and follow-up procedures

Exclusion Criteria:

1. Acute promyelocytic leukaemia (AML subtype M3)

2. With other malignances

3. Failing to acquire a suitable UCB unit

4. With previous history of autologous haematopoietic cell transplantation (auto-HCT), allogeneic haematopoietic cell transplantation (allo-HCT) or chimaeric antigen receptor T-cell therapy

5. With uncontrolled infection intolerant to haplo-HCT

6. With severe organ dysfunction

   • Cardiac dysfunction (particularly congestive heart failure, unstable coronary artery disease and serious cardiac ventricular arrhythmias requiring antiarrhythmic therapy)
   • Respiratory failure (PaO2≤60 mmHg)
   • Hepatic abnormalities (total bilirubin≥2×upper limit of normal [ULN], alanine aminotransferase or aspartate aminotransferase≥2×ULN)
   • Renal dysfunction (creatinine≥2 mg/dL creatinine clearance rate < 30 mL/min)

7. In pregnancy or lactation period

8. With any conditions not suitable for the trial (investigators' decision)