This paper investigates the effect of laser pre irradiation on strengthening of fused silica surfaces. Fused silica surfaces heated evenly with CW CO 2 laser radiation under go in changes including residual compress stress occurred, peak to volley and microcracks decreased, which are observed by polarized microscopy and atom force microscopy. Damage thresholds of fused silica surfaces measured with a Q switched Nd:YAG laser increase by a factor of 1.53 after pre irradiation.