A series of fluorescent polymers with tunable di-color emission, P(NVS) n –NAPHs, were prepared via well-controlled atom transfer radical polymerization (ATRP). Each of the obtained polymers with different molecular weights has a composite emission spectrum comprising a blue component originated from the monomer, 1-(4-vinylstyryl)naphthalene (NVS), and a green component originated from the initiator, 2-(2,3-dihydro-2-(4-methoxyphenyl)-1,3-dioxo-1H-phenalen-7-ylamino)-ethyl-2-chloroacetate (NAPH). The intensity of the blue and green emission bands can be easily tuned by changing the polymer chain length. The blue emission part is enhanced with increasing the molecular weight of the fluorescent polymer in both DMF solution and film state.