Abstract: The pipe leaked in use after five years. The leakage reason of the pipe was analyzed by means of chemical composition analysis, hardness testing, metallographic examination, intergranular corrosion analysis and fracture SEM analysis. The results showed that chromium depletion in heat-affected zone during the welding process and the residual stress led to the pipeline cracking. It was suggested that all of the welding seam should be inspected nondestructively to find corrosion cracks, and the cracks should be grinded and repaired by welding processing, and the residual stress should be eliminated.