The invention discloses a gas type stretcher for rod-shaped metal. The stretcher comprises a main control shell, a supporting plate structure integrated with the main control shell is arranged at thebottom of the main control shell, a fixed plate is fixed to the bottom of the supporting plate structure, a movable space is formed in the main control shell, a limiting hole structure is formed in the side, located in the movable space, of the main control shell, a sealing column is arranged in the side, located in the limiting hole structure, of the main control shell, and a main sealing rubberpad is installed in the center of one end surface of the sealing column. The stretcher is used as technical detection equipment for known metal mechanical properties, a preset air pressure plays a detection role, when the air pressure is greater than the preset air pressure, further compression is avoided, clear detection is realized on the basis of simple equipment and low cost, the using cost islower, the service life is longer and the practicality is higher.