The traditional glass forming using laser ablation in air would produce many kinds of defects such as bulge, debris, crack and scorch. In this paper, we have applied the method of PDMS assisted laser processing to reduce the temperature gradient, heat-affect zone region for achieving crack-free glass ablation. The laser power of 15 W, PDMS thickness of 150 μm and scanning speed of 228 and 342 mm/s were used for ablation to obtain a good quality of cutting surface which was clear, less bugle, no crack and scorch in this technique. The alpha-step measured profile showed that the much reduced bugle height around the rims of groove was about 1.0± 0.5 μm in case of 150 μm poly-dimethylsiloxane (PDMS) thickness while that in air was 15.1 μm. The ANSYS software was also used to analyze the temperature distribution and thermal stress field in air and PDMS ambient during glass ablation. The smaller temperature gradient observed in PDMS-assisted ablation had the smaller heat-affect zone and diminished the crack formation during processing. In contrast, the higher temperature gradient in air induced higher stress for creating crack and scorch on the surface.