Several magnetic fluorescence nanocomposites were presented. The particles exhibit intense fluorescence and large MR T2-weight values with CdSe depositing on Fe3O4 nanoparticles layer-by-layer to form Fe3O4/CdSe nanocomposites. The fluorescence of different layered nanocomposites was studied and the intensity was found to increase greatly with the accumulation of CdSe shell layers from 1 to 3. With the layers addition from 3 to 6, positions of the fluorescent spectra peaks do not move, but become broad. The magnetic properties were investigated and they were still superparamagnetism after the growth of CdSe shells. The nanoparticles are promising for in vivo applications with both fluorescence imaging and MRI.