Life　cycle　inventory　(LCI)　can　be　used　to　quantify　the　energy　input　and　materials　assumption　as　well　as　associated　with　environmental　emission　of　a　product　system　in　their　whole　life　cycle,　and　provide　important　information　to　improve　the　environmental　performance,　to　compare　possible　alternatives　or　to　establish　recommendations　for　action,　product　procurement,　purchase　and　disposal.　Data　flow　balanced　Algorithm　was　built　up　in　terms　of　the　main　flow　and　modeling　the　unit　process　and　flow　chart,　and　LCI　data　compiled　method　were　also　established　based　on　the　recursion　algorithm　of　primary　flows.　Lastly,　a　case　practice　of　iron　and　steel　production　was　carried　out　to　test　the　correctness　of　developed　LCI　calculation　model.