The work aims to study corrosion mechanism of L80 tubing in an Bohai oilfield, which is of important significance to analyze corrosion features of tubing, determine corrosion type, confirm corrosion environment of downhole, assess corrosion extent and recommend anti-corrosion materials. Based on preliminary estimate of macro corriosion morphology of L80 tubing, material analysis was carried out first, then micro-corrosion morphology was analysed. Thirdly, the corrosion product and corrosion extent were analyzed. Finally, electrochemical test was conducted. Physical and chemical properties as well as metallographic structure of L80 tubing were qualified. Corrosion behavior of inner and outer wall was inconsistent, the corrosion behavior of outer wall was uniform and slight while that of inner wall was localized and serious. The corrosion product mainly contained Fe, S, O and C elements, the main ingredients were Fe1-xSx, FeCO3 and Fe2O3. The pitting depth ofouter wall was 15~50 μm while that of inner wall was 80~150 μm, and crack width of inner wall was 80~150 μm. Partial pressure of CO2 and H2S, temperature and water content had vital impacts on the corrosion behavior of L80 tubing. Pitting corrosion and stress corrosion cracking (SCC) of L80 tubing were relatively slight. CO2 and H2S coexist in the downhole of Bohai oilfield, L80 tubing is subject to CO2/H2S electrochemical corrosion, but the pitting corrosion and stress corrosion cracking (SCC) are relatively slight as a whole and L80 tubing exhibits good SSC capacity. According to the study results, L80 tubing is recommended to be used in offshore oilfield.