A　novel　transparent　plate　thickness　measurement　method　based　on　laser　triangulation　with　the　light　compensation　is　put　forward,　and　a　design　of　transparent　plate　thickness　measuring　device　is　based　on　single　laser　displacement　sensor,　which　is　applied　to　correct　the　focal　plane　in　excimer　laser　micromachining　of　transparent　material　based　on　projection　lithography.　Firstly,　the　relationship　between　bending　light　and　transparent　plate　location　based　on　laser　triangulation　method　is　built,　and　the　relationship　between　displacement　of　scattering　light　spot　and　plate　thickness　is　analyzed.　The　changing　rules　of　measuring　results　caused　by　the　distance　between　transparent　plate　and　scattering　base　plate　and　the　position　change　of　scattering　base　plate　are　also　analyzed.　Then　transparent　plate　thickness　measuring　device　based　on　single　laser　displacement　sensor　is　designed.　The　relationship　between　spot　migration　and　transparent　plate　thickness　is　tested,　and　compensation　coefficient　of　polymethyl　methacrylate　(PMMA)　thickness　measured　by　experiments　is　0.441.　Based　on　the　theoretical　analysis　and　experimental　verification,　the　results　show　that　laser　displacement　sensor　readings　are　linear　relation　with　thethickness　of　transparent　plate,　and　the　distance　between　transparent　plate　and　scattering　surface　has　no　effect　on　it.　The　average　absolute　error　of　PMMA　plate　thickness　measurement　is　less　than　0.01mm,　and　the　average　relative　error　is　0.6%,　which　can　meet　the　precision　requirements　for　processing　biochip　of　PMMA　base　by　the　excimer　laser　(KrF,　248　nm)　micromachining　system.　©,　2015,　Science　Press.　All　right　reserved.