The　characteristics　of　weld　shape,　microstructure,　mechanical　properties　and　defects　of　5A90　Al-Li　alloy　joint　by　laser　welding　(LBW)　and　laser　welding　with　filler　wire　(LWFW)　were　studied　and　analyzed.　The　results　indicated　that　the　microstructure　of　joint　by　LWFW　was　fine-grained　layer　and　the　equiaxed　grain　in　most　of　seams,　which　were　similar　to　the　joint　by　LBW.　Compared　with　the　joint　by　LBW,　the　microstructure　of　joint　by　LWFW　tended　to　fine,　and　the　range　of　the　columnar　crystals　zone　was　prone　to　decrease.　The　Microhardness　of　the　joint　by　LWFW　(92.57HV0.2)　was　lower　than　that　by　LBW　(95.65HV0.2),　but　the　uniformity　was　better.　The　ultimate　tensile　strength　of　the　joint　by　LWFW　was　lower　than　that　by　LBW　slightly,　which　reached　to　73.03%　and　79.22%　of　the　base　metal　respectively.　However,　the　elongation　of　the　LWFW　joint　was　higher　than　that　of　the　LBW　joint　significantly,　which　reached　to　38.65%　and　20.38%　of　the　base　metal　respectively.　The　microstructure　and　mechanical　properties　of　5A90　Al-Li　alloy　by　LWFW　were　better　than　that　by　LBW.　The　defects　of　joint　were　mainly　forming　defects　which　were　caused　by　improper　parameters　and　porosity　inside　the　joint,　which　was　caused　by　uncleaned　surface　and　incomplete　penetration.