As an independent disease, aplastic anemia (AA) has been recognized for more than a century. When AA is diagnosed, other non-AA bone marrow failures should be excluded. It is termed as exclusive diagnosis of AA. The exclusive diagnosis of AA is helplessly based on that there is no parameter by which AA can be sensitively and specifically diagnosed now. So further searching for the meaningful diagnostic parameters of AA should be carried on to establish a direct diagnostic protocol of this disease and make it possible to differentiate it clearly from other bone marrow failure disease such as congenenital bone marrow failure, hypoplastic myelodysplastic syndromes, AA-paroxysmal nocturnal hemoglobinuria syndromes, large granules lymphocyte leukemia, clonal cytopenia of undetermined significance, immunorelated pancytopenia, acute hemopoietic arresting and idiopathic cytopenia of undetermined significance. The new markers and technologies being helpful for distinguishing AA from other bone marrow failures should be used in diagnosing AA. Correct understanding and application of exclusive diagnosis is not only related to the correctness of diagnosis and treatment of excluded diseases, but also to the quality of AA diagnosis, treatment and research.