In order to accurately evaluate the service performance of wellbore string materials in gas production and injection wells, and explore the failure mechanism of corrosion and scaling, taking an ancient natural gas production well in Yulin gas field as an example, monitoring experiments such as wellbore fluid analysis, tubing MIT test, downhole coupon weight loss corrosion test, SEM, EDS, XRD, 3 D and other related characterization tests were carried out. The results show that the electrolyte wellbore fluid formed by the dissolution of CO2 in the condensate water with low salinity in ancient natural gas is attached to the surface of N80 carbon steel in the form of water film. Under the condition of high temperature and high pressure, hydrogen depolarization electrochemical corrosion reaction is the main reaction without obvious scaling phenomenon. The corrosion products are mainly FeCO3 crystal. The corrosion products at 1500m are denser, which can inhibit uniform corrosion. However, the maximum depth of local corrosion pit is more than 113μm, which is consistent with the result of severe local corrosion in some well sections tested by MIT. The increase of daily water production at the development late stage will increase the tendency of pipe string corrosion perforation. The experimental results obtained from the application of various corrosion monitoring technologies can provide technical support and theoretical basis for the formulation of anti-corrosion and anti scaling measures for the wellbore string of gas wells.