To assess the safety and efficacy of FLU-BU-MEL as a conditioning regimen for allogeneic hematopoietic stem cell transplantation in patients with untreated MDS-EB or IPSS-R that is intermediate-risk (\>3.5 points), high-risk, or very high-risk. The investigators conducted this clinical trial.There will be three phases to this trial: screening, therapy, and follow-up. A) Screening phase: Qualified patients are screened for trial participation by a medical history, physical examination, laboratory testing, and disease evaluation after providing their informed consent. B) Treatment duration: patients receive allogeneic hematopoietic stem cell transplantation prepped with Flu-Bu-Mel in accordance with the protocol. C) Follow-up period: patients were checked on at the scheduled time to assess safety and efficacy. HSCT conditioning regiment: Flu 30 mg/m2/d d-6 days to d-2 9 (intravenously over two hours), : MEL 50 mg/m2/d intravenously, d-3 to d-2; BU 0.8 mg/kg/q6h d-6 to d-5 (intravenously, over 2 hours per drip). Fludarabine and melphalan do not require a dose adjustment based on body weight; however, if body mass index BMI\> 25, ideal body weight (IBW) should be calculated (as BMI=25), and then determine Busulfan dosage based on corrected body weight (AIBW25). AIBW25=IBW+25% x (actual body weight - IBW)