Abstract: The paper descrides such case that there had been buried oil pipeline being corroded and pierced after operation even with the adoption of cathodic protection. The reason for such case is that the corrosion of pipeline at late period of operation would have a close relation with the poor quality of construction at initial period, and that the cathodic protection was not being applied together with buried pipeline at same time. Thus, the paper points out that the pipe corrosion of pipe-in-pipe thermal insulaton technology is a new topic to be discussed and that the present cathodic protection method and the way of measurement are to be inquired.