The invention, which belongs to the technical field of the optical system design, relates to a millimeter-wave/long-wave infrared common-caliber composite imaging lens. According to the millimeter-wave/long-wave infrared common-caliber composite imaging lens, the long-wave infrared optical system with the wavelength of 8.0 micrometers to 12.0 micrometers and millimeter-wave (8.5mm) antenna are designed to be an integrated body with the common caliber. The common part of two channels is formed by an optical head cover, a main reflector and a sub reflector; the millimeter-wave antenna channel uses the common part to transmit and receive electromagnetic energy; and the long-wave infrared channel is formed by the common part and a correction lens. The composite imaging lens transmits electromagnetic energy and simultaneously receives infrared and millimeter-wave energy, separates the long-wave infrared energy from the millimeter-wave energy, and transmits the energy to an infrared detector and a millimeter-wave detector separately, thereby realizing simultaneous or time-sharing detection of a target.