The　fatigue　property　and　fracture　mechanism　of　TC4　titanium　alloy　joint　during　laser　welding　was　investigated.　It　was　found　that　the　fatigue　life　of　laser　weld　was　longer　than　that　of　the　base　metal　under　low　stress　levels.　However,　the　fatigue　life　of　laser　weld　was　shorter　than　that　of　the　base　metal　under　high　stress　levels.　Fatigue　cracks　originated　in　the　surface　for　base　metal　specimen.　In　the　fatigue　crack　expansion　zone,　numerous　curving　secondary　cracks　and　fatigue　striations　were　found　perpendicular　to　the　direction　of　crack　propagation.　Fissures　at　the　root　of　some　fatigue　striations　were　also　observed.　The　fatigue　cracks　of　the　weld　originated　in　the　pores　in　the　weld　surface,　and　numerous　secondary　cracks　were　straight　and　parallel　near　the　fatigue　resource.　In　the　fatigue　crack　propagation　area　of　the　weld,　small　dimples　were　found　in　fine-grain　zone　and　became　shallow　near　the　columnar　crystal.　Mass　of　micro-shear　sliding　bands　and　shallow　dimples　were　found　in　the　weld　center.　The　fracture　mechanism　of　the　weld　was　formation　of　shear　sliding　bands　and　rupture.