A new method for preparing GRIN (gradient refractive index) polymer rod by using the swollen-gel polymerization technique was fabricated. Monomer pair systems of MMA (methyl methacrylate) with reactive BzMA (benzyl methacrylate) and unreactive BN (bromonaphthalene) and BPAc (benzyl phenyl acetate) were investigated. Two-dimensional refractive index profile of rods were estimated. A high NA (numerical aperture) value of 0.336 in system of MMA/BN = 2/1 was obtained. A good symmetric GRIN rod can be fabricated by using the swollen-gel polymerization. The image with no distortion can be observed through the GRIN rods fabricated by using the swollen-gel polymerization method.