One kind of amidoxime group containing chelating fiber with high adsorption．capacity to Au3+ ion (up to 626.7mg／g，when nitrile group conversion reaches 53.7％) was prepared by treating polyacrylonitrile fiber with hydroxylamine．The relationship between reaction condt-lions，fiber structure and properties was investigated．It is revealed that the decreases in tight-ness and regularity of PAN supermolecular structure are of advantage to raising nitrile group conversion．In the treatment process

the paracrystallite in the fiber begins to be fused at 70℃．The content of amidoxime group in the fiher increases at first then tends to steady value with the increase of hydroxylamine concentration lor reaction time，and does not increase quickly until reaction temperature reaches 70℃．The fiber strength decreases with the increase of reac-tion time，while does not decrease until the temperature is up to 70℃．It is suggested that，in order to prepare a chelating fiber with high amidoxime group content and reasonable mechani-cal property，the reaction should be immediately carried out slightly below 70℃．