The work aims to study the influence law of AC interference on the corrosion behavior of X100 pipeline steel welded joints in simulated solution of Golmud soil by using simulated X100 steel welded joint with different microstructures. Potentiodynamic polarization curve, potentiostatic polarization curve, immersion test and surface analysis technique were adopted to investigate the corrosion behavior systematically. The potentiodynamic polarization curves showed that with the increase of AC current density, the corrosion current density of X100 steel with different microstructures also increased. The cathode controlled by the oxygen-consuming reaction was dominated by hydrogen evolution reaction gradually. Under the interference of alternating current, the corrosion rate of annealed structure, hot-rolled structure and normalized structure was descending. In the potentiostatic polarization test, the annealed structure was more obviously affected by AC interference. The corrosion morphology of X100 steel with different microstructures was mainly local corrosion and there were different degrees of pitting. In addition, the number of corrosion pits in the annealed structure was more and the size was bigger and deeper. Pitting was mostly distributed at the grain boundary of pearlite and ferrite, and a few were distributed inside the pearlite. However, the normalized structure had less number of pitting corrosion and the size was smaller. The hot-rolled microstructure had more granular bainite which was diffusely distributed, and more small pits were distributed in the area where granular bainite aggregated. The X100 pipeline steel with different microstructures has different corrosion resistance. The micro-galvanic corrosion caused by pearlite and ferrite is more serious under AC interference, so the annealed structure has the worst corrosion resistance, while the M/A island in the normalized structure is needle-like and the number of granular bainite is less, so the corrosion resistance is the best. The corrosion resistance of the hot rolled structure is between that of annealed structure and normalized structure.