TA15　alloy　fabricated　by　laser　melting　deposition　was　investigated　at　500　degrees　C　under　tensile　deformation.　The　damage　behavior　of　microstructure　was　analyzed　by　the　real　time　observation　of　the　microstructure　evolution,　microcracks　initiation　and　propagation　using　in-situ　tensile　equipment　fitted　in　the　SEM　chamber.　Finally,　the　mechanism　of　fracture　was　discussed.　The　result　showed　anisotropic　mechanical　properties　in　X-　and　Z-direction.　The　existence　of　columnar　beta　grains　and　its　orientation　to　the　tensile　direction　were　the　major　factors　inducing　the　anisotropic　mechanical　properties.　As　compared　to　Z-direction　specimen,　high　tensile　strength　was　observed　in　X-direction　specimen　due　to　the　resistance　in　slips　propagation　provided　by　the　prior-beta　grain　boundaries　(beta　GBs).　Accumulation　of　the　cracks　at　prior　beta　GB　caused　the　shear　fracture.　In　case　of　Z-direction　specimen,　parallel　orientation　of　prior　beta　GB　and　GB　alpha　with　the　tensile　direction　resulted　in　a　homogeneous　deformation.　The　high　reduction　of　cross　section　showed　the　enhanced　ductile　characteristics　at　high　temperature.