Early detection of circulation tumor cells (CTCs) in breast cancer patients has great clinical relevance. Currently, immunomagnetic microparticles enriched assays require Fe 3 O 4 inner cores, making it difficult to improve sensitivity. In this study, we prepared magnetic nanoparticles with carbon-coated pure iron (Fe@C) acted as the core, Conjugating with EpCAM monoclonal antibody for immunomagnetic nanoparticles(IMPs). IMPs were used in conjunction with immunocytochemistry (ICC) to develop a refined immunomagnetic nanoparticles enriched assay (IMPEA) for detection of circulating tumor cells (CTCs) in breast cancer patients. Compared with nested RT-PCR, this method achieved the same sensitivity, but with a significantly reduced false-positive rate. This method will help find hidden micrometastases, establish clinical stage, and guide individual treatment post-surgery, suggesting potentially significant value in the clinic.This team of investigators prepared magnetic nanoparticles with carbon-coated pure iron as core and conjugated them with EpCAM monoclonal antibody to form immunomagnetic nanoparticles for circulating tumor cell (CTC) detection. Compared with nested RT-PCR, this method achieved the same sensitivity, but with a significantly reduced false-positive rate, paving the way to the development of a tool that enables enhanced detection of micrometastases and post-surgical treatment monitoring.