The invention provides a photographic optical system. The photographic optical system sequentially comprises a first lens (focal length being f1), a second lens (focal length being f2), a third lens (focal length being f3), a fourth lens (focal length being f4), a fifth lens (focal length being f5), a sixth lens (focal length being f6) and a seventh lens (focal length being f7) which are coaxially arranged from an object side to an image side, wherein the first lens has negative focal power and an object side surface being a convex surface; and the seventh lens has negative focal power, and satisfies the following conditions: -1.5<f1/f<-0.5, 1.0<f2/f<2.5, 0.5<f3/f<1.5 , -2.5<f4/f<-0.5, -10<f5/f<-2, 0.2<f6/f<1.2, -2.5<f7/f<-0.4, wherein f is the focal length of the entire system. The photographic optical system with large relative aperture provided by the invention is designed through reasonable surface form optimization, focal power allocation and optical material selection, can provide imaging performance in a low illumination environment, and is clear in imaging.