Abstract: Undigging detection of destroyed spots was carried out on the outer corrosion protection layer of the oil pipeline by RD-PCM detector, its accuracy is 100%. Among them, the welding joint without the corrosion protection treatment and those with unqualified corrosion protection layer was about 80% of the destroyed spots, the others were extrusion. After digging, maintenance and being reburied, the pipeline was detected once more, which show that the pipeline was well protected. Some precautions are also proposed on the fixing of the pipeline.