The pipeline pipe-to-soil potential at Hayilian is up to -2290 mV (CES) and above, which is much higher than the relevant standard. The cause of the high protective potential is analyzed to prevent to prevent the damage to the pipeline due to the hydrogen evolution. Combined with the environment of export pipeline at Hayilian, the external disturbance voltage and current to pipelines are tested and analyzed. At the same time, the potential test is carried out by using the near-reference method, and the influence of high soil resistance which leads IR drop on the negative potential is analyzed. The results show that the export pipeline at Hayilian is not affected by stray current. On the contrary, high resistance of the test circuit is the main cause of the ultrahigh potential; if no power failure occurred to the near-reference coupon, the potential caused by loop resistance R can be reduced by about 500m V, while in case of power failure, the potential will be further reduced by 550Mv, which proves that the pipe-to-soil protective potential shall be measured by combination of near-reference electrode method with current interruption method.