The disclosure discloses an optical imaging system, sequentially includes from an object side to an image side along an optical axis: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens, wherein the first lens has a positive refractive power; the second lens has a negative refractive power, an object-side surface thereof is a concave surface, and an image-side surface thereof is a convex surface; the third lens has a refractive power; the fourth lens has a positive refractive power, an object-side surface thereof is a concave surface, and an image-side surface thereof is a convex surface; the seventh lens has a negative refractive power, an object-side surface thereof is a convex surface; and a total effective focal length f of the optical imaging system and an entrance pupil diameter EPD of the optical imaging system satisfy f/EPD≤0.8.