Abstract: The measurement on fracture toughness of the local brittle zone in heat-affected zone (HAZ) was investigated for three kinds of TM-CP steels with yielding strength 420~460 MPa.It is necessary to an alyzeif the testing results can reflect the fracture toughness of the local brittle zone,because of the complexity of multi-pass welding HAZ.It has been pointed that the section technique should be conducted after the multi-pass welding HAZ fracture toughness tests,the following examinations should be taken.First whether the pre-fatigue crack front is in the target zone is checked.Second whether the ductile crack deviates from the tar-get zone is checked.The fracture toughness gotten from testings could reflect the target zone property if the above requirements are satisfied.The effect of strength mis-matching on fracture toughness for weld HAZ as also discussed by testing results.