In this paper, photoinduced intermolecular charge transfer (PICT) and fluorescence resonance energy transfer (FRET) in donor-acceptor systems have been investigated experimentally and theoretically. We attempt to investigate the natural relationship between FRET and PICT, and reveal the advantages of FRET enhanced PICT. The driving force for PICT in the FRET system equals the reorganization energy, which gives barrier-less charge transfer according to Marcus theory. The rates of PICT in the FRET system can be estimated with our simplified Marcus equation. Our results can promote the deeper understanding of the nature of FRET enhanced PICT, and benefit rational design for the use of the FRET system in organic solar cells.