Abstract: Welding transverse deformation of steel bridge box section bar web plate element brings great difficulty for subsequent straightening and assembly. Based on the thermal elastic-plastic finite element method, the flame straightening of steel bridge web plate element was simulated in ANSYS software, and the simulation results were verified by the measured deformation of actual flame straightening. The simulated values are in good agreement with the experimental values, which proves the effectiveness of flame straightening simulation. The optimization analysis on the parameters such as flame heating speed, heating pass number and heating position was further conducted. The results indicate that the flame correction is more obvious when the flame is heated along the welding seam position; the correction amount of multi-pass heating is bigger than that of single pass heating; reducing the flame heating speed or multi-pass heating along different paths can improve the flame correction efficiency.