The　heavy　section　joints　of　titanium　alloys　welded　in　electron　beam　welding　(EBW)　is　obtained,　and　the　mechanical　properties,　microstructure　and　weld　geometrical　parameters　of　the　joints　are　studied.　The　failure　behavior　and　mechanism　and　the　mismatching　characteristics　of　the　joints　are　defined　in　a　quantitative　manner,　and　the　three　dimensional　residual　stresses　distribution　is　estimated.　On　the　above　bases,　the　methodology,　evolution　principle　and　relative　procedures　on　the　assessment　of　structural　integrity　of　EBW　heavy　section　titanium　alloy　structures　are　drafted.