Abstract: Described in the paper is the technical performance of two kinds of German make detectors with a diameter of 720 mm, one is the ultrasonic detecting pipeline corrosion, the other is a kind of drift decting device, and the site detecting procedure and result of their first application in Lu-Ning Pipeline. Both kinds of detectors can carry out on-line detection. Drift detecting device goes through the pipeline first to make sure if corrosion detector can be used followed by a series of pigging work, for instance, scraping the wax film formed on the pipe's internal surface so as not to reduce the signal quality. Running inside the pipeline with the flow of oil, these types of detectors can perform their detection both automatically and independently, being able to work continuously for 150 km, with all the changes of drifting detected and every defect pointed, located, the data of which are simultaneously recorded in the device and the results are able to be shown through computer calculations. In the 199.22 km long pipeline detection, 600 or so defects were located, most of them were external defects, among 49 of which were 4 mm in depth. Part of the detecion results were verified by open-cut examination. The application of detectors provide reliable and scientific data for the pipeline built to be maintained in a planned way.