The goal of this clinical trial is to evaluate the effectiveness of CD123-CD16 bispecific antibody-modified NK cells in treating patients with CD123-positive relapsed or refractory Acute Myeloid Leukemia (RR AML). It will also assess the safety of this modified NK cell therapy. The main questions： Does the infusion of CD123-CD16 bispecific antibody-modified NK cells induce remission in RR AML patients? What are the safety and potential adverse effects associated with the administration of these modified NK cells? Researchers will administer CD123-CD16 bispecific antibody-modified NK cells to RR AML patients and compare the outcomes to existing treatment options to determine efficacy and safety. Participants will: Undergo lymphocyte-depleting chemotherapy Fludarabine\&Cyclophosphamide from day -5 to day -3 before NK cell infusion. Receive intravenous infusions of modified NK cells at escalating doses: The first three patients will receive 1×10⁷ cells/kg. The next three patients will receive 2×10⁷ cells/kg. The final three patients will receive 4×10⁷ cells/kg. Have NK cell infusions administered every 96-120 hours for a total of three infusions, with each infusion completed within 10 to 15 minutes. Undergo dose escalation with subsequent groups only after confirming the safety of the previous dose group. Have their vital signs (temperature, heart rate, respiratory rate, blood pressure, etc.) monitored before and after each infusion. Keep baseline data records during NK cell infusions. Participate in follow-up assessments to monitor disease remission and detect any adverse events. This trial aims to provide new treatment options for RR AML patients by leveraging the targeted cytotoxic effects of CD123-CD16 bispecific antibody-modified NK cells to achieve disease remission.