In order to obtain a better welding process of corrugated steel web flange plate weldment, with Toudaohe bridge taken as the engineering background, the welding numerical calculation models under three different loading conditions are to be established by using ABAQUS, thus obtaining the changes of temperature field of weldment during the process of welding, followed by a comparison of the longitudinal residual stress distribution of single-sided weldment under different welding sequences, as well as an analysis of the longitudinal residual stress distribution of single-sided weldment and double-sided weldment in the fillet area, with the influence of variable section on the longitudinal residual stress of key details taken into consideration. The research results show that the equivalent residual stress near the welding line is close to the yield stress of Q345 steel, a factor that should not be ignored; meanwhile a reasonable welding sequence helps to reduce the longitudinal residual stress of the single-sided weldment in the corner area; for the double-sided weldment, the stress level of the weld on the first welding side is lower than that of the single-sided weldment, while the stress level of the welding line on the second welding side is higher than that of the single-sided weldment. In order to reduce the longitudinal residual stress in the fillet weld area, it is suggested to adopt the double-sided welding process of an initial welding of the outside of the fillet arc and a subsequent welding of the inside of the arc; moreover, the longitudinal residual stress of key details is negatively correlated with the thickness of flange plate.