The　interfacial　thermal　stress　and　the　bonding　quality　of　GaAs-GaN　wafers　via　thermal　pressures　were　observed　and　analyzed　by　a　scanning　electron　microscope　(SEM)　with　an　electron　backscatter　diffraction　(EBSD)　technology.　Stress　sensitive　parameters,　including　image　qualities　of　Kikuchi　patterns,　crystal　rotations,　lattice　misorientations　and　dislocation　intensities　at　GaAs-GaN　bonding　interface　was　measured　by　EBSD.　The　results　indicate　that　the　wafer　bonding　was　of　high　quality　and　the　thermal　stress　of　bonding　interface　in　the　centre　area　was　smaller　than　that　in　the　edge　areas.　The　influence　regions　of　the　stress　for　GaN　and　GaAs　layers　were　about　100　and　300　nm　in　the　centre　area　and　100　and　500　nm　in　the　edge　area.　Stress　field　displayed　by　EBSD　was　similar　to　that　by　simulation.　The　simulation　and　calculation　indicate　that　the　largest　shearing　and　peeling　stresses　distributed　in　the　edge　area　of　bonding　interface.　The　peeling　stress　played　an　important　role　for　wafer　de-bonding.