The utility model relates to a pipe cutting machine tool field, concretely relates to pipe cutting machine clamping mechanism, comprises a workbench, the fixed axle, the cover is established at fixed epaxial spring, press from both sides tight arm and gasbag, one side of workstation is equipped with the bracing piece, the bracing piece is connected with the fixed axle is perpendicular, it is two to press from both sides tight arm, equal slip cap is located above the fixed axle, the spring is located two outsides that press from both sides tight arm, and the one end that the bracing piece was kept away from to the fixed axle is equipped with the stopper, press from both sides the tight arm clamping jaw that all is provided with inboard relatively, two tight arms of clamp pass through airbag connection, and the both sides of gasbag have two air cavitys respectively, the air cavity is provided with the air vent relatively, be connected with the air ejector between two air cavitys. The utility model discloses a spring and gasbag mutually combine, realize tightly to the clamp of tubular product, avoid tubular product to carry out the displacement.