The present disclosure discloses an optical imaging system including, sequentially from an object side to an image side along an optical axis, a first lens having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; and a fourth lens having negative refractive power. A distance TTL along the optical axis from an object-side surface of the first lens to an imaging plane of the optical imaging system and a distance To along the optical axis from a to-be-captured object to the object-side surface of the first lens satisfy 1