Abstract: For the CTOD fracture toughness test to the offshore pipeline,normally the weld test specimen is taken from a test block that is not flatted in order to ensure the maximum specimen thickness,and due to the presence of the weld pipe curvature,it is in any case a sub-sized one. Owing to the size effect of the CTOD value,there exists relevance between such value and the specimen thickness. Therefore CTOD tests are conducted with specimens taken from four pipes with different sizes and steel types,and the results are comparatively analyzed,showing that the CTOD values from the full-thickness weld specimens are overall better than those from the sub-sized weld specimens.