In order to explore the influence of dynamic DC interference and sulfate reducing bacteria (SRB) and their synergistic effect on the corrosion behavior of X80 steel in electrified railway, the dynamic stray current was applied to X80 steel soaked in SRB by building the indoor simulation experimental device of dynamic stray current. MPN counting method, living / dead cell staining, SEM, EDS, XPS, CLSM and other surface analysis techniques were used to study the effect of dynamic DC interference on the physiological activity of SRB and the corrosion behavior of X80 steel under the combined action of dynamic DC interference and SRB. The results show that the dynamic DC interference has no obvious effect on the growth of SRB in solution. But it has a great influence on the adhesion of SRB and biofilm on the surface of X80 steel. Cathode protection inhibit the adhesion of SRB on the surface of X80 steel and reduce the SRB activity on the metal surface by inhibiting the respiration of SRB, so as to reduce the microbial corrosion of X80 steel. The anodic interference current promote the adhesion of SRB on the surface of X80 steel, and enhance the SRB activity in the biofilm on the metal surface. The corrosion rates of ?400 mV, 0 mV and 500 mV samples of X80 steel in sterilized environment are 0.086 35 mm/a, 0.219 2 mm/a and 0.458 3 mm/a respectively, which are 0.97, 2.46 and 5.15 times of natural corrosion rates. Under dynamic DC interference, the corrosion rate of X80 steel increases greatly. Although the single DC stray current interference time is short, but it has a very serious damage to X80 steel with the accumulation of time. The biofilm formed by SRB can slow down the dynamic DC stray current corrosion of X80 steel to a certain extent, but the combined action of SRB and dynamic DC aggravates the pitting corrosion on the surface of X80 steel.