Abstract: The rear surface defects and impurities of fused silica can absorb the laser irradiation energy strongly, resulting in the high temperature difference and thermal stress. When the thermal stress reaches the tensile strength limit, a brittle rupture will happen in the fused silica. In this study, we preload the rear surface of fused silica to weaken and counteract the damage of the thermal stress by mechanical forces. It can produce continuous changes of the pre-stress. As it is difficult to obtain the stress value in experiment, we measure the central deformation rate to the reverse surface stress distribution and simulate deformation and stress changes by ANSYS. A third harmonic generation laser damage test is utilized to the laser induced damage threshold in different pre-stress conditions. It indicates that the pre-stress 0-50 MPa can improve the laser induced damage threshold obviously, because the 0-50 MPa pre-stress can reduce and counteract the tensile stress produced from the laser irradiation. However, the pre-stress more than 50 MPa can reduce the mechanical properties by coupling effects. The pre-stress 0-50 MPa can increase the laser damage resistance effectively.