Abstract: Corrosion defects can affect the ultimate bearing capacity of pipelines, and X80 pipes are the primary material utilized in long-distance pipeline projects, such as the West-East Gas Pipeline. Consequently, conducting numerical simulation research to predict the ultimate load of X80 oil and gas pipelines containing corrosion defects holds significant engineering significance and value. Based on the characteristic dimensions and corrosion defect data of X80 pipeline, a full-scale numerical finite element model of X80 pipeline is established using commercial finite element software. The numerical model incorporates actual boundary conditions and internal pressure load of the pipeline. Both pipelines without and with defects were analyzed, and the results revealed that the maximum Mises stress occured at the transition between the bottom of the defect and the smooth circular arc surface. The depth and length of the defect exert a mutual influence on the pipeline's ultimate load. Ultimately, a prediction method for the ultimate load of X80 oil and gas pipelines with corrosion defects was proposed. This method was compared and validated with actual test data from X80 pipelines. The results demonstrated that the prediction method exhibited high calculation accuracy and good applicability.