Abstract: The defects of incomplete penetration, incomplete fusion and etc within East pipeline became a critical threat to pipeline safe operation. In order to solve the difficult problem of defect inspection, we carried on triaxial high-resolution magnetic flux leakage inspection test within Northeast crude oil pipeline. It was originally thought that the defects of roof topping, hi-low and etc were the principal factor causing spiral weld defect signal anomaly with the inspection analysis results. Du to this conclusion, triaxial tools could not detect the spiral welding incomplete penetration defects. The authors of this paper put forward the doubtful points with foreign company conclusion, and gave the process of demonstration and experimental verification, also the obtained conclusions, thought that the defects of roof topping, hi-low and etc is not the principal factors causing spiral weld defect signal anomaly. This paper obtained the result different from foreign companys conclusions, updated the knowledge of triaxial high-resolution magnetic flux leakage inspection for spiral weld defect, and broadened the research idea.