Objective To observe the distribution and the effect of the quantum dots(QDs) on mouse abdominal cavity macrophages. Methods The QDs were co-cultured with mouse abdominal cavity macrophages in vitro. The differentiation and effect of the QDs on macrophage ultrastructures were observed under electronic microscope. Results The QDs were enveloped with unit membrane and internalized in the cytoplasm of the macrophage under transmission electron microscope.And it formed vacuolelike structures in the macrophage.There were many lamellar processes on the surface of the macrophage under scanning electron microscope.Conclusion The QDs can promote macrophage activation,and make its surface projection increased.The QDs were internalized by the macrophage, distributed in the cytoplasm, and formed vacuolelike structures enveloped with unit membrane.