The invention relates to a back distribution type front pneumatic chuck which comprises a chuck body, a wedge core sleeve, a retaining cap, three jaws, three sliding bases and three T shaped blocks. The back distribution type front pneumatic chuck is characterized in that an air cylinder body is connected with a base to forma an air cylinder main body, a piston is installed in the air cylinder body and connected with the wedge core sleeve through a push-pull sleeve and a push-pull ring, the wedge core sleeve slides up and down in the chuck body under the driving of the piston, an upper air chamber and a lower air chamber are formed above and below the piston, the base is fixedly connected with an extended valve rod in a thread screwing way, the valve rod and a valve body are connected through a bearing and can rotate relatively at a high speed, and a valve cap is connected with the valve body through a screw. The back distribution type front pneumatic chuck has simple, compact and reasonable structure; since the air cylinder body and the chuck body are connected into a whole and a distributing valve is arranged at the rear part independently, the back distribution type front pneumatic chuck can be successfully installed in a narrow space at the tail part of a machine tool, thereby greatly reducing the labor intensity, shortening clamping time and improving productivity; and in addition, since the clamping force is adjustable, the back distribution type front pneumatic chuck can be matched with numerical control equipment which needs air distribution at the tail part of the machine tool and has limited space at the tail part.