The invention discloses a large-aperture ultrawide-angle low-distortion imaging system comprising a glued lens piece formed by a first lens, a second lens, a third lens and a fourth lens, a diaphragmaperture A, a glued lens piece formed by a fifth lens 5, a sixth lens 6 and a seventh lens 7, an eighth lens 8, a ninth lens 8, a light filter 10 and a photosensitive piece 11 which are arranged fromthe object plane to the image plane in turn, wherein the aperture size of the first lens 1 is D1, the distance between the first lens 1 and the photosensitive piece 6 is TL, the total focal length ofthe optical lens is f, and D1, TL and f meet: 0.2<f / TL<0.3 and 0.6<D1 / TL<0.4. The wide-angle light can be effectively converged and 100-degree ultrawide-angle photographing can be realized; the plastic lens can be used and the processing cost can be reduced; and the positive distortion produced by other lens pieces can be effectively neutralized by the R2 plane so as to guarantee low-distortion imaging.