When the output power of the CO₂ laser machine reaches100W on average, the round focusing point can be formed on the surface of glass by the focusing light path. The laser energy of 10.6μm wavelength is absorbed fiercely by the15μm_thick glass layer on the surface, and the locol stress line distributing is formed. At the same time the quenching mouth is blowing the colder air onto the glass surface, quenching the thermal area quickly. The temperature of the glass surface is higher than the softening point, blowing colder air onto the surface forms the thermal stress concentrtion layer. The glass is disconnected along the cut which is made by mechanic means before cutting, and the crack is smooth. The best pace of the laser thermal stress cutting is 400 mm/s which is testified by the experiment.