The application discloses an optical imaging system. The system sequentially comprises the following components from an object side to an image side along an optical axis: a first lens having refractive power, an image side surface of which is a convex surface; a second lens having negative refractive power; a third lens having refractive power, the image side surface of which is a concave surface; a fourth lens having refractive power; a fifth lens having refractive power, the object side surface of which is a convex surface; a sixth lens with positive refractive power, the object side surface of which is a convex surface; a seventh lens having refractive power; an effective focal length f of the optical imaging system and an entrance pupil diameter EPD of the optical imaging system meet the condition that f/EPD is less than 2; the effective focal length f of the optical imaging system, an effective focal length f1 of the first lens, and an effective focal length f2 of the second lens satisfy 0.1