For optical applications, including lenses, widely used polystyrene (PS) has not received much attention due to its considerably high birefringence. In this study, an efficient method was introduced to compensate for the orientation birefringence of PS through bottlebrush polymers with well-controlled PS graft chains (PS-BBP). PS-BBP were synthesized by ring-opening metathesis polymerization of norbornene-terminated PS macromonomers produced via atom transfer radical polymerization. Blend-film samples were then prepared by mixing linear PS and PS-BBP. One of the blend samples with a specific ratio of linear PS to PS-BBP (30:70) demonstrated extremely low orientation birefringence of |Δn| ∼3.9 ×ばつ 10-4 even under 120% strain. In addition, the blend samples preserved almost the same refractive indices as linear PS, possessing the transparency required for optical polymers across the visible-wavelength range. The obtained PS blend could be utilized as an optical material with excellent optical properties.