A novel drug carrier based on SiO2-coated silver nanoparticle aggregates and antitumor drug is successfully synthesized. The surface-enhanced Raman scattering (SERS) spectra of the antitumor drug in living cells are obtained. By using silver nano-aggregates as SERS substrates instead of dispersed silver particles, a great improvement of SERS signal intensity is achieved. It is found that the chemical stability of the drug carrier can also be increased with the existence of SiO2 shell. The adsorbing effect between antitumor drug 9-aminoacridine (9AA) and silver particles is investigated to optimize the SERS signal. The core/shell structure of the drug carrier is characterized by ultraviolet-visible (UV-Vis) spectroscopy and transmission electron microscopy (TEM) pictures. The experimental results show that the drug carrier offers biocompatibility, stability, and high SERS activity, holding the potential for realizing the intracellular drug tracing.