Low　temperature　toughness　of　deposited　metal　made　by　three　types　self-shielded　flux-cored　wires　used　for　X70　pipeline　has　been　investigated,　by　analyzing　macroscopic　and　SEM　morphology　of　impact　fracture,　microstructure　and　statistics　of　inclusion.　The　results　showed　that　low　temperature　toughness　of　deposited　metal　of　three　wires　was　significantly　different.　No.3　wire　has　highest　toughness　with　an　impact　absorbing　energy　average　value　of　330　J　at　-40°C,　while　the　toughness　of　No.1　wire　is　the　lowest,　whose　impact　absorbing　energy　average　value　is　only　113　J　at　-30°C.　Differences　of　inclusions　and　microstructure　of　deposited　metal　were　the　main　reason　for　significantly　different　toughness.　Uniform　and　fine　equiaxed　grains　and　small　inclusions　uniformly　and　dispersedly　distributed　in　deposited　metal　are　beneficial　to　improve　the　low　temperature　toughness.