A nanocomposite composed of ZnO and poly (methyl styrene-co-chloro methyl styrene) P (MSt-co-CMSt) by in situ polymerization method were prepared successfully. For this purpose, firstly, the zinc oxide surface was treated with 3-(trimethoxysilyl) propyl methacrylate (TMSPMA), a silane coupling agent, and following that this functionalization nano-ZnO particle was reacted with PMSt to prepare PMSt-grafted TMSPMA-ZnO. The resulting PMSt-grafted TMSPMA-ZnO was brominated with N-bromosuccinimide and coupled with 1-hydroxy-2, 2, 6, 6-tetramethyl-1-piperidinyloxy (TEMPO-OH) to produce an NMRP macroinitiator (PMSt-TEMPO/nano-ZnO). The well-controlled graft polymerization of 4-chloromethyl styrene (CMSt) with macroinitiators were carried out to produce nanoparticles based-ZnO (PMSt-co-PCMSt)/zinc oxide nanocomposite). Properties, crystal structure, and the morphology of (PMSt-co-PCMSt)/zinc oxide nanocomposite was studied using H-1-NMR, FT-IR, XRD, TGA, DSC, TEM, and UV-Vis spectroscopy. The results of FT-IR investigation and observations of TEM images represented clear and strong evidence for the preparation of PMSt and PMSt-co-PCMSt with spherical morphology of ZnO nanoparticles. The synthesized nanocomposites can be utilized a compound to attenuate the UV irradiation in the range of pointed wavelength.