In recent years, driven by metagenomics sequencing technology, it has been found that compositional changes and diversity changes of gut microbiota are related to the occurrence of hematological malignancies. Gut microbiota affects the development of the hematopoietic system and the risk stratification of hematological malignancies. Microbial translocation plays an important role in and blood stream infection. Gut microbiota imbalance and blood stream infection affect the therapeutic effect of hematological malignancies. Probiotics and fecal microbiota transplant can restore the diversity of gut microbiota.