An improved technique to fabricate PMMA/Ag core-shell nanocomposite via a two-step procedure is reported. The procedure includes an improved particle surface treatment and an improved, subsequent Ag reduction reaction strategy. Well-dispersed PMMA/Ag core-shell nanoparticles with uniform particle size distribution were successfully fabricated using this improved technique. Different functional group treatment on the PMMA particle surface led to an electronically graded transition from the covalent bond of PMMA core to the metallic bond of silver shell. The improved fabrication technique thus allows a highly tailorable size of PMMA core and controllable thickness of Ag shell, which is crucial to producing a tunable plasmon resonance signal to different bio-/chem-environments.