Fluorescent carbon nanoparticles (f-CNPs) were successfully grafted with polystyrene by employing a “grafting from” method via reversible addition-fragmentation chain transfer polymerization (RAFT). The detailed polymerization kinetic studies showed that the grafting polystyrene polymerization from the f-CNPs surface via RAFT was living-controlled. The synthesized f-CNP-g-PSt nanocomposites with different grating lengths via RAFT could fluoresce like f-CNPs. At the same time, the synthesized f-CNP-g-PSt nanocomposites could be easily processed into fibers by electrospinning. The fibers could still fluoresce at the appropriate excitation wavelength. The f-CNP-g-PSt nanocomposites synthesized via RAFT feature good processability may be applied as luminescent plastic.