Effect of Stem Cell Infusion Time on aGVHD in Patients With Hematological Malignancies Post UCBT

Inclusion Criteria: * Definite diagnosis of malignant hematologic disease before transplantation, age, gender and race are not limited; * Participants were required to have achieved complete remission with negative minimal residual disease (MRD) prior to transplantation; * Participants who are proposed to receive sUCBT for the first time; * Eastern Cooperative Oncology Group (ECOG) score 0-2; * No serious organ failure and active infection; * Voluntary open randomized controlled study to observe whether the time of stem cell infusion affects the occurrence of aGVHD after transplantation; * Each subject must sign an informed consent form (ICF) indicating that he/ she understands the purpose and procedures of the study and is willing to participate in the study; in view of the subject's condition, if the participant's own signature is not conducive to the treatment of his/her condition, the ICF will be signed by the legal representative. Exclusion Criteria: * Those with severe organ dysfunction or disease, such as severe disease and dysfunction of the heart, liver, kidneys and pancreas; * Any life-threatening disease, physical condition, or organ system dysfunction that, in the opinion of the investigator, may compromise participant safety and put the results of the study at unnecessary risk; drug-dependent individuals; participants with uncontrolled psychiatric disorders; and individuals with cognitive dysfunction; * Participants in other clinical studies that may affect aGVHD within 3 months; * Those whom the investigator considers unsuitable for enrollment (e.g., those who anticipate that patients will not be able to adhere to the examination and treatment due to financial and other issues).