The　Intergranular　Corrosion　(IGC)　properties　of　Al-xMg-0.6Mn(x=3,　4,　5,　6　and　7)wt.%　alloys　were　studied　using　the　mass　loss　test.　The　mass　loss　test　results　of　the　alloys　annealed　at　100-300°C　for　1h　indicated　that　the　alloys　with　3　and　4%　Mg　were　resistant　to　IGC.　While　the　mass　loss　values　of　the　6　and　7%　Mg　alloys　were　increased　to　IGC　severe　sensitive　region,　and　then　abruptly　fallen　to　the　IGC-resistant　region　with　the　increasing　temperature.　The　mass　loss-temperature　curve　of　5%　Mg　alloy　was　actually　located　between　them.　After　isothermal　annealing,　the　mass　loss　results　indicated　a　stabilization　temperature　of　the　alloys　with　5,　6　and　7%　Mg　appeared　at　the　temperature　beyond　220°C,　250°C　and　270°C,　respectively.　Furthermore,　below　the　stabilization　temperature　10-20°C,　it　was　observed　a　type　of　＇special　mass　loss　curve　＇　in　so-called　transition　region　that　was　showed　a　quick　mass　loss　increasing　to　sensitization　region　and　then　a　decrease　to　the　IGC　resistant　region　with　a　prolonged　annealing　time.　To　explore　the　＇special　curve＇　in　transition　region,　the　TEM　observation　of　Al-7Mg　alloy　annealing　at　250°C　was　conducted,　which　indicated　the　sensitization　resulted　from　the　continuity　of　β　phase,　while　the　descending　to　the　IGC　might　to　be　attributed　to　the　spheroidization　of　β　phase.　©　2017　Trans　Tech　Publications,　Switzerland.