The thermal-mechanical model of transparent optical materials induced by high-power continuous laser is set up and the precise resolution of transient temperature field distribution induced by laser is obtained through resolving the 3-dimensional heat conduction equation using integral-transform method. On the base of the above analysis, the thermal stress field transient distribution induced by laser is worked out. Taking fused silica irradiated by 1.315 μm high-power chemical oxygen-iodine laser (COIL) as an example, the fused silica temperature field and thermalstress field transient distributions irradiated by COIL laser are calculated and the laser induced damage mechanism is analyzed further. The calculation result shows that the laser induced damage is mostly melt damage in the areas where temperature exceeds melt point of fused silica. Because fused silica has a fine thermal stability, the thermal stresses induced by the temperature ununiformity are small relatively. The theoretical analyzing result is in accordance with the relative experimental result, so the laser irradiation effect model proves correct.