The test of high temperature and high pressure and electrochemical technology were utilized to investigate the effects of temperature on the corrosion behavior of L80 carbon steel in CO₂ containing natural seawater. The Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and X-Ray Diffraction (XRD) were used to characterize corrosion scale. The results show that firstly, corrosion rate of L80 carbon steel increases and then decreases with increasing temperature in the liquid phase, and the maximum value lies at 90℃, while this variation trend is completely opposite to that in the gaseous phase, a corrosion product layer is mainly composed of FeCO₃, anion selective permeability of FeCO₃ product film and the absorption of Cl^- on steel surface prompt the CO₂ corrosion on the L80 carbon steel surface, the electrochemical properties of corrosion scale formed at 90℃ in liquid and gaseous phases further prove the test results described above.