Bone marrow cytology refers to the process of taking bone marrow fluid from a patient by bone marrow aspiration to make a blood smear, which is stained and observed under a microscope to see if the morphology of various bone marrow hematopoietic cells is normal. Generally speaking, the report card of bone marrow cytology examination first looks at whether the sampling, smear and staining are good and determines whether the degree of bone marrow proliferation is normal. The degree of bone marrow proliferation is judged according to the ratio of red blood cells to nucleated cells in the bone marrow. In normal people, bone marrow proliferation is active or significantly active. If there is an abnormally active degree of bone marrow proliferation, it is often common in acute leukemia and chronic leukemia. If bone marrow hematopoiesis is diminished or if bone marrow hematopoiesis is severely diminished, aplastic anemia is the most common. It is also important to look for normal red lineage hyperplasia, normal granulocytic hyperplasia, and normal megakaryocytic hyperplasia; and also to see if the percentage of primitive cells exceeds normal. Through the examination, a general judgment can be made on the bone marrow cytology pattern, and a clear diagnosis can be made for most hematologic diseases.