The electrochemical properties and microstructures of CO₂ corrosion scale formed on N80 carbon steel at 3 MPa and different temperatures in stratum water with saturated CO₂ were investigated. The impedance results showed that the compactness of corrosion scale increased and the diffusion process decreased with increasing temperature; when temperature reached to 200 ℃, the diffusion impedance of corrosion scale decreased, indicating that the diffusion of ions in the scale became easy. electrochemical impedance spectrum (SEM) results revealed that the scale is of a double-layer structure, the length of the scale decreased with temperature increasing. Observation of the microstructure of the sample surface after removing the corrosion scale, showed that many big holes existed in the sample surface at low temperature,which became small and finally turned into uniform corrosion with temperature increasing. When temperature reached to 200 ℃ the holes became bigger again, indicating the corrosion extent promoted furthermore.