The　ultra-thin　plate　(thickness　＜　0.1　mm)　is　widely　used　as　the　raster　plate　in　the　high-precision　collimator,　but　the　welding　induced　distortion　is　the　main　problem　restricting　its　application.　In　this　study,　the　effect　of　laser　power　on　the　welding　deformation　of　an　ultra-thin　steel　plate　during　pulsed　laser　welding　was　studied　by　means　of　both　numerical　simulation　and　experiment.　A　three　dimensional　thermal-elastic-plastic　FE　analysis　was　conducted　to　predict　the　temperature　field　and　distortion　of　the　ultra-thin　steel　plate.　The　thermal　and　mechanical　material　properties　used　in　this　simulation　all　followed　the　non-linear　relations　as　a　function　of　temperatures.　Meanwhile,　a　pulsed　laser　welding　experiment　was　carried　out,　the　temperature　field　was　measured　by　a　pyrometer,　and　the　distortion　was　measured　by　a　laser　displacement　sensor.　The　results　showed　that　the　model　prediction　was　consistent　with　the　experimental　measurements　results.