Due to the complex submarine environment, submarine pipeline steel often faces serious corrosion risk. Through potentiodynamic polarization technology and AC impedance technology, the effects of hydrostatic pressure, mass concentration of dissolved oxygen and growth days of sulfate reducing bacteria (SRB) on the electrochemical corrosion behavior of X70 pipeline steel in simulated solution in the South China Sea were investigated. Combined with electron microscope characterization technology, the corrosion morphology was analyzed, and the mechanism of the corrosion behavior of X70 steel under the coexistence of three environmental factors was clarified. The results show that the self corrosion current density of X70 pipeline steel in the experimental environment inoculated with SRB is twice that of sterile steel; under the pressure of 0~3.5 MPa, the corrosion degree first intensifies and then slows down; when SRB and dissolved oxygen coexist, the presence of oxygen inhibits the number of facultative anaerobic bacteria SRB, thus inhibiting corrosion.