Abstract: Laser cutting is widely used in thin-walled parts, temperature is a greater influence on machining accuracy. In view of the instantaneous change of temperature field and elastic-plastic deformation during laser cutting of thin-walled parts, proposed a computational method of thermal losses based on Fouriers law. The influence of hot deformation to temperature field and deformation were analysed. The temperature field was changed 13.8% by calculating specific heat capacity varies with temperature. It is one of the key precipitants of temperature field, which is not negligible. Heat-conduction resulted in an 49.58% decrease in temperature, which is one of the major heat loss that has influence on the processing quality. The effect of temperature field on radiation and convection is less than 0.1 ℃. Deformation of radiation and convection is negligible when machining accuracy lower than micron-scale accuracy.