LED optical system capable of uniformly emitting light and lamp

The LED optical system comprises a reflection cup and a lens, the lens is fixed on the light emitting side of the reflection cup, the lens is provided with a light inlet face and a light outlet face, the light inlet face is located on the side close to the reflection cup, the light outlet face is located on the side away from the reflection cup, a center incidence hole is formed in the middle of the bottom face of the reflection cup, and the center incidence hole is communicated with the light outlet face. It is assumed that the reflection cup is divided into two symmetrical parts by a section passing through the center incidence hole, in a section map, a section curve l1 of the side wall of the reflection cup is a straight line, or the section curve l1 of the side wall of the reflection cup is an inverse arc line, two end points of the section curve l1 are a point A and a point B, the length of a straight line l2 formed by connecting the point A and the point B is L, the straight line l2 is located on the ou