Design: This is a multicenter, single-arm, prospective clinical trial. Eligible patients will receive the following conditioning regimen: thiotepa 5 mg/kg/day on Days -10 to -9; busulfan 3.2 mg/kg/day on Days -8 to -6; fludarabine 30 mg/m²/day on Days -6 to -2; and rabbit anti-thymocyte globulin (rATG) 1.5-2.5 mg/kg/day on Days -5 to -2. Hematopoietic stem cell infusion will be performed on Day 0. Graft-versus-host disease (GVHD) prophylaxis will include cyclosporine A (CsA), mycophenolate mofetil (MMF), and methotrexate (MTX). The primary endpoint of this study is 1-year relapse-free survival (RFS). Inclusion Criteria: Age 55-70 years (inclusive). Diagnosis of high-risk AML , include relapsed/refractory AML or CR MRD+ or ELN22 adverse risk group .Relapsed/refractory AML defined as at least one of the following: recurrence of leukemia cells in peripheral blood or bone marrow blasts \>5% after complete remission (CR), failure to achieve remission after two courses of standard induction therapy, relapse within 12 months after consolidation therapy, relapse after 12 months that is refractory to conventional chemotherapy, multiple relapses, or persistent extramedullary leukemia）. Scheduled to undergo haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Adequate organ function. Eastern Cooperative Oncology Group (ECOG) performance status ≤2. Written informed consent obtained. Exclusion Criteria: Unwillingness or refusal to accept the study treatment protocol. Presence of donor-specific anti-HLA antibodies. Known human immunodeficiency virus (HIV) infection. Active hepatitis B or C, or chronic active hepatitis. Uncontrolled active infection at the time of enrollment. Any other condition deemed by the investigator as unsuitable for study inclusion.