Azacitidine in Combination With Venetoclax Treatment for MRD Positive Post Allo-HSCT AML/MDS Patients

Inclusion Criteria: 1. Patients between 18 years old and 65 years old. 2. Patients with AML or MDS diagnosed according to WHO diagnostic criteria. 3. Patients who received allogeneic hematopoietic stem cell transplantation and achieved complete remission. 4. MRD was positive after transplantation, MFC \> 0.1% and / or fusion gene and gene mutation (WT1 \> 0.6%, AML1-ETO \> 0.4%, others \>1%). 5. ECOG body status score 0-2. 6. Patients with expected survival time \>=3 months. 7. Good organ function level: ANC (neutrophil absolute value \>=1.0x10\^9/L; PLT \>=30x10\^9/L; HB \>=80g/L; Tibil \<=1.5 ULN; ALT / AST \<=2.5 ULN; bun / Cr \<=1.5 ULN; LVEF \>=50%). 8. Patients who have received any anti-tumor treatment (including radiotherapy, chemotherapy, surgery or molecular targeted treatment) for more than 4 weeks from the end of the previous treatment. 9. Patients with no GVHD and no previous history of 3 or more degrees of aGVHD. 10. Patients who voluntarily participate in the clinical trial, understand the research procedure and can sign the informed consent in writing. Exclusion Criteria: 1. Patients with severe cardiac insufficiency and EF lower than 60%; or patients with severe arrhythmia who could not tolerate super pretreatment. 2. Patients with activity of aGVHD or extensive cGVHD. 3. Patients with BCR/ABL positive. 4. Patients who were previously known to be resistant to azacytidine or dessicabine or venetoclax. 5. In patients with severe pulmonary insufficiency (obstructive and / or restrictive ventilation disorders), the researchers evaluated the patients who could not tolerate the super pretreatment scheme. 6. Patients with severe liver function impairment and liver function indexes (alt, TBIL) more than 3 ULN were evaluated as intolerant of super pretreatment. 7. In patients with severe renal insufficiency, the renal function index (CR) is more than 2 times of the upper limit of the normal value (ULN), or the 24-hour creatinine clearance rate (CR) is less than 50ml / min, the researchers evaluated that they could not tolerate the super pretreatment scheme. 8. In patients with severe active infection, the researchers evaluated that they could not tolerate the pretreatment. 9. Patients who had allergic reactions or serious adverse reactions in the previous use of pretreatment related drugs could not be included in the study. 10. Patients with hematological recurrence (bone marrow smear: proportion of primordial cells \>=5%) or any extramedullary recurrence. 11. Other reasons why the researchers could not be selected.