In order to study the influence of derrick corrosion on bridge safety, the influence of derrick damage on the seismic performance of through derrier arch bridge under different corrosion degrees is researched based on the simulation test analysis method of Midas Civil. The effective cross-section of the derrick after corrosion is calculated by using the corrosion and sheilding effect of the steel bar, and the model based on the cross-sectional size of the effective derrick is established for simulation calculation. The results show that: 1) The increase of the corrosion rate of the derrick will lead to the increase of the natural vibration frequency of the arch bridge, while the longitudinal displacement of the arch bridge decreases and the vertical displacement increases under the action of earthquakes; 2) The corrosion of the derrick has a certain impact on the mechanical properties of the arch bridge, especially the Z-direction shear force and Y-direction bending moment. The results can provide a theoretical basis for the actual engineering seismic design.