The invention discloses a suction cup type reducing installed camera. The top end of a double-end stud is connected with a connecting block of a camera body in threaded and sleeved modes, and the end portion of the bottom end of the double-end stud is fixedly connected with the small end face of the upper end of a conical suction cup. A plurality of circular rings hooping the suction cup are arranged on the outer surface of the suction cup from top to bottom. A conical cover is arranged above the suction cup in a covering mode, the bottom end of the double-end stud is sleeved with the cover, and the cover and the suction cup are coaxial. The cover is downwards pressed through an adjusting nut at the bottom end of the double-end stud. An installation base comprises a circular bottom plate, sliding threaded sheets and a conical plug screw. A sliding groove is formed in the bottom plate, and the camera body is fixed to the bottom plate. Each sliding threaded sheet comprises a threaded sheet portion, a neck portion and a sliding block portion which are sequentially connected, wherein the threaded sheet portion is located on the surface of the bottom plate. The camera can be installed on a smooth wall conveniently, quickly and firmly, decoration is not damaged, and the camera can be flexibly replaced with cameras with different thread diameters.