Abstract: In this paper, a new method, the fuzzy mathematics theory, to assess the corrosion and protection trends of pipeline is put forward. The authors consider that the trends of soil corrosion, original pipe-to-pipe potential, coating quality and validity of cathodic protection can be judged by this theory. At the same time, the calculation procedure to each factor can be confirmed and the theory and procedure can also be clarified, which can provide an effective method for corrosion and protection trends of pipeline assessment on buried long-distance pipeline.