Abstract: Through field investigation and indoor analysis on "pipe in pipe" pipeline, it is found out that electrochemical corrosion caused by water entering into insulation coating is the major reason for pipe body corrosion. If the water entered into insulation coating reaches saturation, there will be light corrosion in pipe body while the insulation coating showing half-wet and half-dry situation, the corrosion of the section will be serious. In order to solve this problem, sacrificial anode set in jacket pipe will control the corrosion effectively. This scheme has been used in Jiao Qing pipeline for 8 years and has got evident anti-corrosion result.