The　C　1s　and　O　1s　electrons　in　polymethyl　methacrylate　etched　by　different　incident　laser　intensities　are　analysed　by　x-ray　photoelectron　spectroscopy.　The　results　show　that　when　the　incident　laser　fluence　increases　gradually,　the　percentage　of　carbon　atoms　in　C-C　bonds　decreases　while　the　one　in　carbonyl　group　(C=O)　and　alkoxy　group　(C-O)　increases,　and　the　percentage　of　oxygen　atoms　in　C=O　bonds　increases　while　the　one　in　C-O　bonds　decreases.　Based　on　the　analysis　of　the　chemical　structure,　the　energy　level　transition,　energy　diversion,　and　dissociation　of　bonds　are　theoretically　examined,　which　is　consistent　with　the　experimental　results.