1, bone marrow examination can be used for the diagnosis of hematopoietic system diseases, such as the differential diagnosis of leukemia, the differential diagnosis of various kinds of anemia, multiple myeloma and thrombocytosis or thrombocytopenia diseases with definite diagnostic significance. 2, certain infectious diseases, such as infective endocarditis, bone marrow culture can help to improve the positive rate of the diagnosis of the disease, in the case of Plasmodium and black fever protozoan infection, bone marrow examination can help to detect the protozoan and clear diagnosis. 3.In the case of certain malignant tumors, bone marrow examination can determine whether there is bone marrow metastasis, because bone marrow is a good site for metastasis of many malignant tumors, lung cancer, breast, stomach and prostate cancer are prone to bone marrow metastasis, and bone marrow examination can find the corresponding tumor cells. 4.It is used for bone marrow stem cell culture, karyotype examination, immunological typing test of bone marrow cells, etc. 5.It can exclude some secondary factors leading to hematological system damaging diseases, such as: systemic lupus erythematosus, hypersplenism .