The invention relates to a longitudinal-wave-mode electromagnetic ultrasonic helical-guided-wave transducer for out-of-pipeline detection, belonging to the technical field of ultrasonic testing in non-destructive testing. The transducer comprises a yoke, a holding structure, a walking support structure, a ripping bar structure, a permanent magnet and a coil. The transducer is characterized in that the yoke is arched; the upper side of the outer arc surface of the yoke is connected with the holding structure; two lateral planes of the yoke are connected with the walking support structure; the ripping bar structure is connected with the walking support structure; the permanent magnet is connected with the inner arc surface of the yoke and is arched; and the inner arc surface and the outer arc surface of the permanent magnet are opposite to each other, and the inner arc surface is connected with the coil. The transducer provided by the invention can produce electromagnetic ultrasonic guided waves propagated along different directions of a pipeline so as to realize generation of spiral guided waves in any direction of the pipeline and detection of pipeline defects in any direction.