The invention relates to a three-degree-of-freedom conversion system and method for different signal antennas in a vacuum environment, belongs to the technical field of mechanical engineering, and tosolve existing technical problems, the system is arranged in a vacuum tank and a vacuum environment is provided; a PLC controller, a first servo driver and a first servo motor are sequentially connected with a translation transmission mechanism, and the translation transmission mechanism is fixed at the top of the vacuum tank; the translation transmission mechanism, a T-shaped connecting plat, anelectronic control tilting table, a second servo motor and a second servo driver are connected in sequence, and the second servo driver is connected with a first servo driver; the electric control tilting table is connected with a bending plate, a side surface of the bending plate is connected with an electronic control rotating table, the electronic control rotating table is connected with a third servo motor, the third servo motor is connected with a third servo driver, the third servo driver is connected with the second servo driver, and the electronic control rotating table realizes the rotation of a signal antenna yz plane; and the electronic control rotating table is connected with an L-shaped connecting plate, and a lower surface of the L-shaped connecting plate is connected with asignal antenna clamp.