The　crack　initiation　and　propagation　in　on-board　packaging　solder　joint　during　thermal　fatigue　test　was　investigated　by　experimental　and　numerical　method　together.　In　this　experiment　the　lead-less　resistance　of　3216　and　the　PCB　of　FR4　were　selected.　And　two　kinds　of　land　shapes　and　two　kinds　of　solder　materials　(including　SnPb　eutectic　solder　and　lead-free　solder　SAC305)　were　considered.　Some　conclusions　are　drawn　from　the　study:　during　thermal　fatigue　test　there　exist　three　typical　locations　where　the　crack　often　initiates　in　the　solder　joint.　And　the　crack　initiation　mostly　occurs　at　the　corner　portion　between　the　resistance　and　the　solder,　which　meets　well　with　the　simulating　results　of　the　distribution　of　inelastic　strain　in　solder　joint　during　thermal　fatigue　test.　Moreover　the　lead-free　solder　joint　has　a　longer　thermal　fatigue　lifetime　than　SnPb　eutectic　solder　joint.　And　crack　growth　velocity　is　larger　in　the　solder　joint　with　a　smaller　land　shape.　These　can　also　be　proved　by　the　equivalent　inelastic　strain　created　in　solder　joint.