Photoswitchable fluorescent polymer nanoparticles (PFPNs) were constructed from an aggregation induced emission (AIE) based fluorogen and a photochromic spiropyran-linked amphiphilic copolymer via a simple co-precipitation method. Possessing the reversible photoisomerization property and high fluorescence resonance energy transfer (FRET) efficiency, not only did the designed spiropyran-linked amphiphilic copolymer provide the PFPNs with excellent long-term stability (～5 weeks) in aqueous media, but also it could both efficiently and reversibly switch on/off the fluorescence emission of the AIE-based fluorogen upon irradiation with UV and visible light. It is worth noting that the high contrast dual-color characteristics written with PFPNs as rewritable fluorescence patterning can be tuned by altering the wavelength of the irradiation light. Moreover, the resultant PFPNs were successfully applied for intracellular dual-color imaging due to their outstanding cell-membrane permeability and rapid photo-responsiveness, as well as excellent repeatability properties.