Steel plate girders with trapezoidal corrugated webs have been used widely over the last years around the world in many roadways and railway steel bridges as they can introduce several important advantages compared with plate girders bridges with flat web. The study in this paper presents a numerical investigation of flange buckling behavior using the FE software ABAQUS and studies the effect of slenderness ratio of the flange and corrugated web on the bending moment capacity and the flexural behavior of trapezoidal corrugated web steel plate girders built-up from high-strength steel (HSSs). Firstly, the linear buckling analysis has been carried out to obtain the local flange buckling coefficient using the general equation of stresses and the stresses obtained from the numerical results, then the ultimate bending moment has been obtained from the nonlinear buckling analyses. The numerical results showed that the flange slenderness ratio and web slenderness ratio play a major role in controlling the bending moment capacity of corrugated web plate girders. Finally, some recommendations have been listed to help structural engineers to design corrugated web bridge girders efficiently.