Abstract: According to corrosion problem in oil pipeline, carried out analysis in the aspect of corrosion effect on pipeline from soil micro-organism, physical & chemical properties and AC current, established corrosion grading regression equation and gradated pipeline corrosion strength based on areas. It is concluded from coupon test that the corrosion on buries pipeline relates generally with soil's water content, specific resistance, soil's weight by volume, and natural potential, pH value and ion's comprehensive contents, its corrosion strength can be predicted by calculation of grading regression equation; in the area affected by AC current, pipeline's ground potential is much higher than natural potential; AC current is liable to have corrosive potential drift to active area, changes the form of metal polarization curve and thus increases the density of passive current. In light of investigation and analysis to corrosion mechanism, cathodic protection was introduced to long distance pipeline on the basis of corrosion strength gradation and ideal protective result was get.