Stressed lap polishing technology is a new large and deep asphericity astronomical polishing mirror. Because the diameter of astronomical mirror is larger and larger, the asphericity is deeper and deeper, we develop the stress lap technology, it can actively deform the lap surface to become an off-axis asphere according to different lap position on mirror surface and different angle of lap. The curvature is different not only on different position, but also on different direction, so the classical large polishing lap cannot keep the lap surface with the aspherical mirror surface when it moves and spins on the mirror surface. The classical small polishing tool not only can get high frequency error on the mirror surface, but also has slow polishing speed. The stressed lap is just enough to solve these problems. Compared with traditional polishing methods, it has high polishing speed and natural smooth. It is computer-controlled polishing technology, using it the authors can polish a deep aspherical mirror just like polish a spherical mirror. This paper introduce our stressed lap and how to apply it to ??910 mm, with F/2 paraboloidal mirror and its testing result. Next step, the authors will develop this technology to polish the off-axis aspherical segment.