Diarrhea after bone marrow transplantation for leukemia may be caused by simple rejection reaction or bacterial infection, first of all, avoid eating stimulating food, secondly, take antidiarrheal drugs or antibacterial drugs, and if it is rejection reaction, it should be strengthened immunosuppressive treatment. 1. Diarrhea after bone marrow transplantation may be caused by rejection reaction, and may be accompanied by fever, skin rash, liver function impairment and other symptoms. At this time, the first step is to eat light, easily digestible food such as porridge. Antidiarrheal drugs such as montelukast can be used for targeted treatment, while strengthening immunosuppressive therapy, such as methylprednisolone, cyclosporine and so on. 2. After leukemia bone marrow transplantation, in order to prevent rejection reaction, immunosuppressive drugs will be used. At this time, the intestinal immunity is low, easy to be infected with bacteria, thus causing diarrhea. At this time, oral probiotics such as Bacillus subtilis capsules can be used to regulate the microecology of intestinal flora. Antibacterial drugs such as norfloxacin capsules can also be applied. The symptoms of diarrhea in post-transplant patients may evolve very rapidly and require early medical attention. All of the above medications should be used under medical supervision.