Abstract: In this work, one-pot green synthesis of a novel kind of water-compatible fluorescent molecularly imprinted polymer nanoparticles for selective optosensing of paracetamol was developed via macromolecular assembly of an amphiphilic fluorescent copolymer and in-situ photocrosslinking. An amphiphilic photo-crosslinkable and fluorescent copolymer containing carbazole groups was first synthesized which could co-assemble with paracetamol (PCM, template molecule) and photoinitiator in aqueous solution. The obtained photo-crosslinkable fluorescent nanoparticles were then crosslinked triggered by UV-irradiation, generating the hydrophilic and fluorescent molecularly imprinted polymer nanoparticles (FMIP nanoparticles) in aqueous media. The whole procedure was carried out at mild working condition, which is facile, green, and energy-saving. The resulting FMIP nanoparticles showed high selectivity toward PCM and obvious fluorescence quenching, induced by template-binding, in water and were a kind of efficient fluorescent chemosensor for the sensing of PCM. A wide linear range over PCM concentration from 4~1000 μM with a detection limit of 1.0 μM has been demonstrated using FMIP nanoparticles as chemosensor. Moreover, a rapid response of less than 2 min has been demonstrated. Finally, such chemosensor based on FMIP nanoparticles was also successfully employed for the detection of PCM in commercial PCM tablets as well as urine samples