Abstract: Magnetic Flux Leakage(MFL) in-line inspection tools was developed to detect metal loss resulted from corrosion in the early days. With the development of tool design, sensors, and electronics, MFL tools can identify and sometimes size many types of pipeline defects and features. This paper briefly introduced the principle of MFL in-line inspection, then analyzed the advantages of advanced high-resolution axial magnetizing MFL tools with Tri-Axial sensor technology, and discussed how to identify pipeline anomalies and pipeline structure features using the Tri-Axial MFL data.