Abstract: A 316L stainless steel ammonia pipeline in a certain power plant cracked during operation. The causes of pipeline cracking were analyzed using methods such as macroscopic observation, chemical composition analysis, metallographic examination, scanning electron microscopy and energy spectrum analysis. The results show that the crack of the pipe extended from the inner wall to the outer wall, presenting a transgranular fracture characteristic, and the crack was dendritic morphology, consistented with the characteristics of stress corrosion cracking. There was Cl element in the corrosion products, and under the combined action of restrained tensile stress and corrosive medium, stress corrosion cracking occurred in the pipeline.