Abstract: On the basis of the given potential along pipeline and current distribution equations, the test method on a limited length of pipe section for surface resistivity of coating, that is decay factor method and polarization potential current density method, has been put forward. When coating surface resistivity test on a longer pipeline is conducted, the pipeline can be divided into several sections to calculate it with polarization potential and current density. In this paper, the relation between cathodic polarzation potential and protective potential of pipeline is discussed and the influence factor of bigger error of current test in pipeline is analyzed.