Abstract: By binding a monoclonal antibody BDI-1 to polystyrene magnetic micospheres using physical and chemical methods together, a kind of immunomagnetic microspheres (IMMS), which can specifically bind target cells and give it magnetic response, was sucessfully constituted. The results of indirect immunofluorescence and cell binding suggest that IMMS can effectively bind target cells while do not have nonspecific binding activity. The influence of antibody added and the ratio between IMMS and cells were also studied. After purging cancer cells from bone marrow of mice with IMMS, the cancer cells were effectively removed while most of the bone marrow cells were recovered.