An optical imaging system includes a first lens which has refractive power, a second lens which has refractive power, a third lens which has a convex object-side surface, and an inflection point is formed on an image-side surface thereof, a fourth lens which has refractive power, a fifth lens which has a convex object-side surface, and a sixth lens which has refractive power and an inflection point is formed on an image-side surface thereof, and wherein the first to sixth lens are sequentially disposed from an object side.