The invention discloses a handheld pneumatic press mounting gun and aims at providing a pneumatic press mounting gun which is easy, convenient and fast to operate, high in safety and large in concentrated impact force. The handheld pneumatic lining press mounting gun is achieved through the following technical scheme that high-pressure air flow is divided into two ways, one way of the air flow achieves energy gathering through a circular array oblique hole in the tail portion of an end cover (3), the end cover is driven to conduct the circular motion, Laval rotating air flow is sent into a gunbarrel dynamic pressure cavity, and an impact piston (5) impacts a piston impact rod (10) along a gun barrel sliding pipe channel through a piston bearing (6). The other end of air flow passes through a cone circular array busbar oblique hole of a conical air cylinder (4) and enters a piston bearing end direction circular array hole, Laval high-pressure concentrated air flow impacting a piston impact rod spring seat is formed, high-pressure energy gathering air flow for impacting the piston impact rod to move along the gun barrel sliding pipe channel in an accelerated manner is formed again,a piston impact rod end direction lining punch head (11) is pushed at a high speed, a pillar at the front end of the end direction impact lining punch head penetrates into a lining, and a lining workpiece is perpendicularly pressed into a lining workpiece inner hole.