Multiple myeloma is a malignant transformation occurring in the plasma cell stage, which has three main elements: malignant plasma cells, malignant plasma cells secreting monoclonal M protein, malignant plasma cells and secreted monoclonal M protein together leading to some tissue and organ damage. Therefore, the diagnosis of myeloma should start from these three aspects, as follows: 1. For the detection of malignant plasma cells, mainly through bone marrow aspiration, bone marrow biopsy, and then smear and pathological section to observe the morphology of malignant plasma cells, in addition, through immunological examination, such as loss cell examination as well as immunohistochemical examination, to determine that the plasma cells are abnormal plasma cells; 2. For the examination of monoclonal M protein, mainly including serum protein electrophoresis, immunofixation electrophoresis, and free light chain detection to detect whether it is normal immunoglobulin or abnormal immunoglobulin, which is M protein; 3. Related organ and tissue damage mainly refers to bone destruction, pathological fracture, renal failure, etc. Therefore, multiple myeloma can be diagnosed from the damage of these target organs.