According to internal pressure effect and without internal pressure effect, the temperature field, thermal stress, strain and the damage of the combustion chamber case under the laser irradiation, are calculated and analyzed respectively, based on the finite element analysis software ANSYS. Analysis results show that, the distribution of the shell temperature field and beam power is identical, and the maximum temperature is at the center of spot. The maximum stress is not in the center, but is located in the flare edg. If the shell absorption of laser power density is lager than 1 000 W/cm2 , the stress of the shell will be greater than limited stress and the shell will soften. In the presence of internal gas pressure condition, shell stress produces a local focus, along the circumferential surface by laser spot center axis region crack probably. Compared with no internal pressure shell, the stress and deformation produced by the shell with internal pressure are greater. In order to achieve the same damaging effects, in the circumstances of exist internal pressure, the laser radiation intensity can be appropriately reduced.