Abstract: Corrosion was observed on the 3Cr steel tubing of a gas injected well in western oilfield. The corrosion causes of the tubing were analyzed by macroscopic inspection, mechanical property measurement, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. The results show that under the nitrogen injection drive condition, dissolved oxygen corrosion mainly occurred in the inner and outer walls of tubing, and dissolved oxygen corrosion and crevice corrosion mainly occurred in the pin end face of the tubing. The corrosion of tubing was caused by the mismatch between the tubing material properties and the corrosion environment in actual service, which was ascribed to the formation of oxygen corrosion environment in the inner and outer walls and end face of tubing due to the oxygen contained in the injected nitrogen.