The　in-situ　measurement　of　the　stress　evolution　at　the　anode　and　cathode　interfaces　of　the　Cu/3.0Ag0.5Cu/Cu　solder　joint　at　current　density　of　4　x　10(3)　A/cm(2)　was　investigated　by　X-ray　diffraction　technique.　Results　indicate　that　the　stress　evolution　is　a　very　complicated　process　at　the　cathode　and　anode　interfaces,　which　mainly　includes　four　stages.　Firstly,　the　metal　expansion　effect　led　to　the　rise　of　the　compressive　stress　at　the　interfaces.　Secondly,　the　stress　relaxation　reduced　the　compressive　stress.　Thirdly,　the　EM　effect　promoted　the　compressive　stress　at　the　anode　interface　and　turned　the　tensile　stress　to　compressive　stress　at　the　cathode.　Finally,　the　stress　was　relieved　by　the　formation　of　the　whisker　and　hillock　at　the　cathode　and　the　tensile　stress　at　the　cathode　continued　to　increase.　It　is　found　that　a　uniform　Cu6Sn5　intermetallic　compound　was　formed　at　the　anode　interface　after　polishing　the　solder　joint.