This study is a single center, prospective, single arm exploratory clinical trial that includes patients with hematological malignancies who are indicated for allogeneic hematopoietic stem cell transplantation (allo HSCT) but lack suitable donors. This project plans to use human leukocyte antigen (HLA) mismatched donors. Ultimately, a HLA mismatched allo HSCT transplantation plan will be established to improve the disease prognosis of these patients and truly enter the era of "everyone has a donor".