Abstract: The recognition mechanism of Rhodamine B (RB) with single-stranded DNA and double-stranded DNA in the absence and presence of colloidal gold has been investigated by using the titration of UV-Vis spectroscopy. The results indicate that a groove binding may occur between RB and DNA in the absence and/or presence of colloidal gold. Besides, it is also observed that the presence of colloidal gold can significantly facilitate the interaction between DNA and the ligands.