Abstract: Taking the in-line corrosion fatigue test of the Korla-Shanshan oil pipeline as an example, the paper introduces the test process. The testecthe pipe material, was API X65 ϕ610×7.1 mm line pipe, the test procedure was that the sample was periodically loaded with artifical seawater until welded seam of the sample fractured. The analysis on the mechanics, metallography, corrosion and fracture was made. The result showed that the fracture was induced by the stress concentration, the fatigue fracture easily arosen at the base metal with poor ductility, and the angle of root bead was of great importance.