This paper presents the synthesis of aqueous CdTe QDs embedded silica nanoparticles by reverse microemulsion method and their applications as fluorescence probes in bioassay and cell imaging. With the aim of embedding more CdTe QDs in silica spheres, we use poly(dimethyldiallyl ammonium chloride) to balance the electrostatic repulsion between CdTe QDs and silica intermediates. By modifying the surface of CdTe/SiO(2) composite nanoparticles with amino and methylphosphonate groups, biologically functionalized and monodisperse CdTe/SiO(2) composite nanoparticles can be obtained. In this work, CdTe/SiO(2) composite nanoparticles are conjugated with biotin-labeled mouse IgG via covalent binding. The biotin-labeled mouse IgG on the CdTe/SiO(2) composite nanoparticles surface can recognize FITC-labeled avidin and avidin on the surface of polystyrene microspheres by protein-protein binding. Finally, the CdTe/SiO(2) composite nanoparticles with secondary antibody are used to label the MG63 osteosarcoma cell with primary antibody successfully, which demonstrates that the application of CdTe/SiO(2) composite nanoparticles as fluorescent probes in bioassay and fluorescence imaging is feasible.