Charge transfer (CT) at the interfaces between titanium dioxide (TiO2) and gold (Au) is investigated by surface-enhanced Raman scattering (SERS) spectroscopy probed by a sandwiched molecule 4-mercaptobenzoic acid (4-MBA). For the first time, the contribution of surface plasmon resonance (SPR) to CT is studied by tuning the surface plasmon absorption of Au nanorods (NRs) from 530 nm to 793 nm. Moreover, the degrees of CT in the TiO2-MBA-Au assemblies are calculated and the maximum degree of CT is obtained when the excitation laser wavelength is resonant with the SPR absorption of the assemblies. Accordingly, we propose a CT pathway in these semiconductor-molecule-metal assemblies, and the mechanism by which SPR contributes to the CT at the interfaces is discussed. This study has established a simple and effective way of studying the influence of SPR on interfacial CT by using SERS, which is beneficial for further investigations on interfacial charge transfers. Our findings will have significant importance for the improvement of photoelectric devices and photocatalytic efficiency.