A novel fluorescence resonance energy transfer (FRET) system has been designed for the Cu2+ ions detection with optical visual assays. In this FRET reaction, the biocompatible, green luminescent monodisperse phenol formaldehyde resin nanoparticles (PFR NPs) synthesized by a simple hydrothermal method were used as the acceptor and the luminescent CdTe quantum dots (QDs) were selected as the donor. By the layer-by-layer method, the polyelectrolyte (PEI/PSS/PEI) were absorbed alternately on the surface of the PFR NPs. As a result, the amino groups were stably modified onto the surface of the PFR NPs. In the presence of 1-ethyl-3-(3-dimethly aminopropyl) carbodiimide (EDAC) and N-hydroxysuccinimide (NHS), the carboxyl groups coated CdTe QDs prepared by using mereaptoactetic acid (MA) as the stabilizer in water solution were coupled to the surface of amino group functionalized PFR NPs to obtain novel FRET nanocomposites. Owing to the sensitive quenching effect of Cu2+ ions on CdTe QDs and effective energy transfer from CdTe QDs to PFR NPs, the as-prepared FRET nanocomposites were utilized to monitor Cu2+ ion with optical visual detection at room temperature within 1 min. This nanoparticle-based FRET probe should promote further development of other nanocomposites for Cu2+ ion detection in the environmental field.