The invention discloses an additive manufacturing mechanism, an additive manufacturing device and an additive manufacturing method. The additive manufacturing mechanism comprises a welding gun, a box body and a friction forging shaft, wherein the welding gun is vertically connected to one side of the box body, and the welding gun is a coaxial hot wire TIG welding gun; the friction forging shaft is rotatably and vertically connected to the interior of the box body, and the lower end of the friction forging shaft penetrates out of the box body; and a transmission mechanism for driving the friction forging shaft to rotate is arranged in the box body. According to the additive manufacturing mechanism, the additive manufacturing device and the additive manufacturing method, high-efficiency additive manufacturing is realized on the basis of an HiTIG welding gun; the problem of the forming of many complex structural parts is solved, the machining procedures are greatly reduced, and the machining period is shortened; and the traditional metal forming mode is changed, the friction forging is carried out in the machining process, so that the mechanical properties of the parts are improved, and the defect that the surface smoothness of the parts formed by the additive manufacturing technology is not high is effectively overcome. The mechanism and the device can work for a long time and can be used for machining some large-scale complex parts.