A　modified　Polyacrylonitrile　(PAN)　fiber　containing　amidoxime　groups　and　its　fiber-Fe　complex　with　ferric　ions　were　prepared,　then　their　mechanical　and　thermodynamic　properties　were　investigated　in　this　study.　The　results　showed　that　the　breaking　strength　and　elongation　at　break　of　the　PAN　fibers　gradually　decreased　with　the　amidoximation　increasing.　The　mechanical　properties　of　the　fiber-Fe　complex　depended　on　its　Fe　content.　Small　amount　of　ferric　ions　coordinating　with　the　fibers　had　a　negative　effect　on　their　breaking　strength　and　elongation　at　break,　but　high　concentration　of　ferric　ions　could　impart　excellent　mechanical　properties　to　the　fiber　due　to　the　crosslink　generated　by　the　intermolecular　complexation.　DMA　results　also　showed　that　the　molecular　construction　of　amidoximated　PAN　fiber　with　high　conversion　of　nitrile　groups　had　experienced　serious　damage,　but　which　was　significantly　recovered　by　coordinating　with　high　concentration　of　ferric　ions　due　to　the　bridged　effect.