Abstract: I-steel composite beams with corrugated steel webs exhibit notable characteristics including high degree of intensification, convenient construction and excellent stability. In order to clarify the bending performance of these beams, this paper conducted numerical simulations on a bridge to reveal the bending bearing mechanisms under various load conditions. This involved considering the steel strengthening effect, the steel-concrete interfacial slip effect and the bending contribution of corrugated steel webs. The continuous strength method was used to propose the calculation formulas for the ultimate bending capacity of I-steel composite beams with corrugated steel webs under different failure modes, and the calculation formulas were verified through model tests. The results indicated that, at the ultimate state, the strain distribution in the bridge deck slab and the upper and lower flanges of the steel beam conformed to the plane section assumption. The longitudinal strain in the corrugated steel webs exhibited a linear distribution along the height, with the tension side near the lower flange entering the phase of steel tensile strengthening. The contribution of the web to bending resistance should not be disregarded. The shear connection degree exhibited a certain influence on the ultimate bending capacity of I-steel composite beams with corrugated steel webs, with higher shear connection degrees resulting in increased bending capacity. Existing standards tended to be conservative in calculating the ultimate bending capacity of I-steel composite beams with corrugated steel webs. The ultimate bending capacity calculation method proposed in this paper, which considers the steel strengthening effect, the steel-concrete interfacial slip effect and the bending contribution of corrugated steel webs, is consistent with experimental results. The method accurately reflects the bending capacity of I-steel composite beams with corrugated steel webs and improves design calculation accuracy.