Backside　grinding　is　the　most　commonly　used　technique　in　silicon　wafer　thinning.　The　grinding　damage　may　cause　degradation　of　mechanical　property　and　induce　residual　stress.　In　this　paper,　bugle　test　is　proposed　to　apply　to　ground　wafer.　Before　the　experimental　work　starts,　the　theoretical　model　needs　to　be　built.　A　numerical　model　is　also　adopted　to　verify　the　applicability　of　the　theoretical　model,　and　the　results　turns　out　the　theoretical　model　only　works　for　films　with　thickness　to　radius　(t/r)　larger　than　1/20.　With　the　existence　of　residual　stress,　the　accuracy　needs　to　be　improved　by　modifying　the　theoretical　model　or　introducing　new　iterative　algorism.