The　phase　transition　of　Copper-tungsten　films　deposited　on　Si　(100)　and　Al2O3　substrates　took　place　by　means　of　in　situ　annealing　in　vacuum　chamber　at　different　temperatures.　X-ray　diffraction　(XRD)　and　the　polarization　phase　shift　technique　were　employed　to　characterize　the　microstructure　and　residual　stress　of　Cu-W　films,　respectively.　The　results　indicated　that　the　two　successive　but　distinctive　stages　of　phase　transition　appeared　with　the　change　of　annealing　temperatures,　i.e.,　W　(Cu)　solution　formation　and　two-phase　crystalline　(W　and　Cu)　structure　formation.　The　relationship　between　phase　transition　and　residual　stress　was　investigated,　the　tensile　stress　was　caused　during　phase　transition,　whereas　it　was　released　with　crystalline　growth.