Laser cutting of liquid crystal display (LCD) glass substrate is a complex light-induced heat process, in which the temperature plays a vital role. In fracture controlled laser cutting technology, thermal stress is used to induce fissure and break the LCD glass substrate. In order to guide the actual thermal stress laser cutting, as well as reduce the blindness and improve the quality in the cutting process, a numerical simulation is proposed for laser cutting LCD glass substrate. The distribution of temperature is obtained by using finite element analysis software ANSYS. A temperature field numerical simulation is established as laser cutting LCD glass substrate. The effects of laser power and spot diameter on the temperature field are studied and the relationship is obtained. A good cutting profile is obtained in experiment with the help of the numerical simulation results.