Hematopoietic stem cell transplant-associated thrombotic microangiopathy is a severe complication with poor prognosis. Its pathogenesis is complex,and the manifestation is endothelial injury in the kidney and other organs. Recent studies demonstrate the role of complement activation in tissue damage. Tissue biopsy,monitor of blood pressure,de novo thrombocytopenia,de novo anemia and lactate dehydrogenase could be useful for early diagnosis. Therapeutic options remain limited. Withdrawal of offering agents such as calcineurin inhibitors is necessary. Eculizumab seems to be an effective drug with good outcomes.