A new ratiometric fluorescence probe is constructed for the detection of rifampin (RIF). Amino-modified silicon nanoparticles (SiNPs) and mercaptoundecanoic acid capped gold nanoclusters (MUA-AuNCs) are self-assembled into nanocomposites, showing dual fluorescence emissions, respectively, at 440 and 615?nm under a single excitation of 300?nm. The morphology, surface chemistry and optical properties of the nanocomposites are finely investigated through transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), UV?vis absorbance, dynamic and steady state fluorescence spectroscopy. Owning to rich hydroxyl groups, RIF can bind with MUA-AuNCs though hydrogen bonds resulting in the red fluorescence quenching. But the SiNPs keep their own blue fluorescence stable, which can act as an internal reference for ratiometric detection. By means of the ratio I615/I440, the linear relationship is established in the range from 0.1 to 5 ?M with the detection limit of 0.04??M. In addition, the synchronous and asynchronous fluorescence 2D correlation maps have been created to in-depth study the relative detecting mechanism.