The　microstructure　of　electron　beam　welded　joints　of　TC4-DT　titanium　alloy　was　analyzed　by　optical　microscope,　and　the　microstructure　characteristics　of　different　position　in　the　joint　were　also　analyzed.　The　crack　propagation　path　and　its　growth　rate　were　investigated　on　the　joint　samples,　which　the　initial　crack　appeared　at　different　location　of　the　welded　joints.　Based　on　the　microstructure　characteristics　of　the　welded　joints,　the　influences　of　the　weld　microstructure　on　fatigue　crack　growth　behavior　were　discussed.　The　results　show　that　there　are　differences　in　the　microstructure　for　electron　beam　welded　joint　along　penetration　depth.　The　fatigue　crack　propagation　resistances　of　the　weld　fusion　zone　and　heat　affected　zone　were　higher　than　that　of　the　base　metal,　and　the　crack　propagation　path　of　the　joints　gradually　tended　to　base　metal　zone.　The　influence　of　the　crack　propagation　path　offsets　on　crack　growth　rate　was　finally　discussed　in　the　paper.