Materials capable of displaying strong ratiometric fuorescence with Förster resonance energy transfer (FRET) processes have attracted much research interest because of various chemosensor and biomedical applications. This review highlights several popular strategies in designing FRET-OFF/ON mechanisms of ratiometric fuorescence systems. In particular, the developments of organic and polymeric FRET materials featuring aggregation-induced emission-based luminogens (AIEgens), supramolecular assemblies, photochromic molecular switches and surfactant-induced AIE/FRET mechanisms are presented. AIEgens have been frequently employed as FRET donor and/or acceptor fuorophores to obtain enhanced ratiometric fuorescences in solution and solid states. Since AIE efects and FRET processes rely on controllable distances between fuorophores, many interesting fuorescent properties can be designed by regulating aggregation states in polymers and supramolecular systems. Photo-switchable fuorophores, such as spiropyran and diarylethene, provide drastic changes in fuorescence spectra upon photo-induced isomerizations, leading to photo-switching mechanisms to activate/deactivate FRET processes. Supramolecular assemblies ofer versatile platforms to regulate responsive FRET processes efectively. In rotaxane structures, the donor-acceptor distance and FRET efciency can be tuned by acid/base-controlled shuttling of the macrocycle component. The tunable supramolecular interactions are strongly infuenced by external factors (such as pH values, temperatures, analytes, surfactants, UV-visible lights, etc.), which induce the assembly and disassembly of host-guest systems and thus their FRET-ON/FRET-OFF behavior. In addition, the changes in donor or acceptor fuorescence profles upon detections of analytes can also sufciently alter the FRET behavior and result in diferent ratiometric fuorescence outputs. The strategies and examples provided in this review ofer the insights and toolkits for future FRET-based material developments.