In this work we firstly used partially thiolated polyamidoamine (PAMAM) dendrimer to replace CTAB molecules on the surface of gold nanorods (GNRs) by round-trip phase transfer ligand exchange, thus eliminating their cytotoxicity and improving their biocompatibility. The dendrimer-modified gold nanorods (dGNRs) were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV-vis spectrometer, thermogravimetric analysis (TGA) and Fourier transformation infrared (FTIR) spectroscopy. The results indicate that dGNRs were successfully prepared.