Gradient refractive index (GRIN) polymer optical rods were fabricated by the swollen-gel polymerization technique. The mechanism and preparation conditions of the swollen-gel polymerization were investigated. The effects of initiator concentration, swelling temperature, polymerization temperature and monomer feed ratios on the optical properties of the GRIN polymer rods were studied. To reduce the swelling time, two different kinds of initiator were compared. The gradient refractive index profiles of the plastic rods were estimated. The image observed through the GRIN polymer rod was also examined.