Laser　dry　etching　using　a　248　nm　KrF　excimer　laser　was　investigated　for　polydimethylsiloxane　(PDMS)　chips　surface　irradiation.　Examination　of　the　morphology　in　relation　to　ablation　depth　was　emphasized,　and　a　heat　conduction　model　of　laser　photothermal　interaction　with　PDMS　surface　was　established.　The　transmittance　and　absorbance　of　PDMS　at　248nm　were　validated　clearly　using　UV-vis　spectrum　measurements.　The　influence　of　laser　pulse　number　on　the　ablation　morphology　and　depth　during　dry　etching　was　also　analyzed.　The　results　showed　that　with　the　increase　of　pulse　number,　the　heat　accumulation　effect　around　the　etched　hole　was　obvious,　and　the　ablation　residue　increased.　The　ablation　depth　also　increased　with　the　pulse　number.　When　the　pulse　number　was　200,　the　etching　depth　reached　36.8　μm.　This　work　provides　a　feasible　basis　for　laser　direct　etching　of　PDMS　microfluidic　chip　channels　and　will　promote　the　development　of　microfluidic　chip　fabrication.　©　2022　SPIE.