A new method for preparing light-focusing plastic rod with gradient refractive index (GRIN) profile was fabricated by using the swollen-gel polymerization technique. Monomer pair systems of methyl methacrylate (MMA) with reactive benzyl methacrylate and unreactive bromonaphthalene, benzyl phenyl acetate, benzyl salicylate, triphenyl phosphate, and dibromobenzene were investigated. It was found that refractive index difference and numeric aperture (NA) values of MMA with an unreactive agent are larger than those of a reactive agent system, and a high NA value of 0.336 in a system of MMA/BN = 2/1 was obtained. A distortion-free image can be observed through GRIN rods fabricated by using the swollen-gel polymerization method. Optical characteristics of the GRIN rod were also investigated.