The optimization of antireflection (AR) structures of polymer composed of an ordered array of tapered pillars was studied. An anodic porous alumina mold with precisely controlled tapered holes was prepared and used for photoimprinting of the polymer. The reflectance of the obtained AR polymer structures with conical pillars was evaluated through the measurement of transmittance. Among the AR structures with pillars with various slopes, those with a gradually changing slope exhibited the lowest reflectance. The fabrication process will be effective for the formation of an AR surface with minimized reflectance over a large sample area.