Poly(N-vinylisobutyramide) (PNVIBA) macromonomer was synthesized by free radical polymerizafion of N-vinylisobutyramide in the presence of AIBN and using p-chrolomethylstyrene as end capping agent．The molecular weight of PNVIBA can be controlled based on the process of prepared NVIBA oligomers by changing concentration of 2-mercaptethanol．The PNVIBA macromonomers exhibit remarkable thermosensitive properties for temperature change in aqueous solution．The PNVIBA grafted polystyrene(PNVIBA-g-PSt) polymeric nanoparticles were prepared by the free radical dispersion copolymerization of PNVIBA macromonomer and styrene in ethanol or ethanol/water mixed solvents．The effects of molecular weight and concentration of the macromonomer and composition of solvents on the particle size and morphology of the PNVIBA-g-PSt nanoparticles were studied．Changing macromonomer concentration and reaction condition could control the particle size in diameter and morphologies of the nanoparticles．