Abstract: In high power CO2 laser the infrared material output-coupler window inevitable absorbing resonant laser energy will produce non-uniform temperature field distribution,and also cause output coupler window to generate thermal distortion,which is called the output-coupler window thermal effect.Thermal effect would change resonant Q-factor,and influence laser stability and output beam quality.So accurate temperature field and thermal distortion field analysis is the key to resolve these problems.In this article semi-analytical solution is introduced to study output coupler window non-uniform temperature field distribution and thermal distortion field distribution under the CO2 laser operated at stable TEM00 mode.Fortunately the research method and obtained results have universality,which can be applied to analyze temperature field and thermal distortion field with axial symmetry thermal models.