This is a prospective single-arm study. Patients with high-risk AML or MDS aged between 18-70 years old will enroll in the study. They will be given hypomethylating agents (azacytidine 32mg/m2 or decitabine 5mg/m2) for 5 days and venetoclax 400mg/d for 7 days after allogeneic hematopoietic stem cell transplantation. The maintenance therapy will start from 60th days posttransplant, repeated every 28 days until up to 1-year posttransplant. The 1-year leukemia-free survival rate，1-year cumulative recurrence rate, and 1-year overall survival will be analyzed.
The main objective of the study is to evaluate the efficacy and safety of maintenance therapy with hypomethylating agent and Venetoclax to improve leukemia free survival for high-risk myeloid malignancies after allogeneic hematopoietic stem cell transplantation .