Abstract: The corrosion cause of a water injection pipeline was analyzed using methods such as component content testing, chemical composition analysis, X-ray diffraction analysis, thermogravimetric-mass spectrometry analysis, infrared spectroscopy analysis, gas chromatography-mass spectrometry analysis and sulfate reducing bacteria detection. The results show that the organic components in the water injection pipeline were mainly hydrocarbons, while contained substances such as lipids, amines, alcohols and olefins. The inorganic components were mainly iron oxides, ferrous carbonate and sand. The pipeline contained a large amount of sulfate reducing bacteria. With the assistance of sulfate reducing bacteria, corrosion under scale occurred, ultimately led to corrosion of the water injection pipeline.