The invention discloses a lens and an LED warning lamp. The lens is used for carrying out light distribution on an LED light source. The lens comprises an annular body. The inner side face of the annular body is a non-upright up-down asymmetric incident face, the outer side face of the annular body is a convex hook face, a light emitting face is formed, light rays irradiated from the incident face to the light emitting face are emitted from the light emitting face, and the included angle between the emitted light rays and the radial direction of the annular body is smaller than or equal to 20 degrees. The LED warning lamp comprises a base, a main circuit board, a light source board provided with LED lamps, a lampshade and the lens. The regulatory requirements for the warning lamp can be met, the lens is small in radial size and high in light emitting rate, the size of the warning lamp can achieve large-scale compression and be ultrathin compared with a traditional warning lamp, the number of the adopted LED lamps can be smaller, and no heat dissipation structure needs to be added. According to the lens, 360-degree uniform light emitting can be achieved, the lampshade does not need to be improved by being additionally provided with prism structures on the inner and outer surfaces, and therefore the machining difficulty and the production cost are reduced.