Provided are a resin composition and an optical film formed by using the same, and more particularly, a resin composition including 85 to 95 parts by weight of a matrix copolymer resin including an alkyl(meth)acrylate-based unit, an acryl-based unit containing a benzene ring, and a (meth)acrylic acid unit, and 5 to 15 parts by weight of a polymer resin having a molecular weight range of 150,000 to 1,000,000 and an optical film formed by using the composition. A resin composition according to the present invention may provide a protective film for a polarizing plate having excellent heat resistance and toughness as well as excellent optical properties, and thus, an optical film formed by using the resin composition of the present invention may be used in information electronic devices such as display devices for various applications.