Abstract: A transverse excitation magnetic flux leakage (MFL) inline detector, with a diameter of 711 mm, was developed in response to the difficulty in detecting axial metal loss defects of long-distance oil and gas pipelines. Linked by the driver and the recorder, the transverse excitation MFL inline detector is mainly composed of a support system, a drive system, a magnetization system, a sensor system, and an acquisition system, etc. With excitation design of auxiliary magnetic poles, the magnetization system of the transverse excitation MFL inline detector can, in addition to meeting the magnetization saturation requirement of the pipeline wall thickness, improve the magnetization effect, reduce the MFL field gradient at the sensor position, and enhance the quantification accuracy for defects. Traction test and industrial application verification were conducted on a new pipeline transverse excitation MFL inline detector, and the results indicate that, the data signals of axial grooves and axial cracklike defects, which are acquired by the transverse excitation MFL inline detector, are clearer compared with the axial excitation MFL detector. This may inevitably contribute to the improved detection accuracy and detection rate of axial defects, as well as the great engineering significance for detecting and identifying axial pipeline defects.