In the process of aluminum profile extrusion forming, the uniformity of mold profile extrusion velocity at the exit mainly by training room, room shape, size and working with the length of the control. Work is also called the sizing with belt, it is vertical mold working face in profile extrusion die and to ensure the quality of extrusion products shape, size and surface of the section. Because of working with frictional resistance, can adjust the metal flow velocity in the training room, room shapes and sizes given conditions, a reasonable design work with length, each part can effectively increase the section of metal flow velocity uniformity, so as to reduce the additional stress in the process of extrusion and the residual stress in workpiece after extrusion, prevent deformation and cracking of profiles.