Abstract: In order to study the influencing factors of the external prestressing incremental change of the composite box girder with corrugated steel webs during bending failure process, the destructive model test of the bending capacity was carried out, and the finite element model was established. Based on the comparisons of experimental data and finite element theoretical values, the validity of the numerical model was verified. The influence of various parameters on the external prestress increment was carried out according to the numerical model. The research showed that the effects of concrete strength on the stress increment of external prestressed tendons was positively correlated; the effects of reinforcement ratio and strength of the normal steel bar, initial effective stress, external prestressing tendon area and shear-span ratio in the tension zone on the stsress increment of external prestressed tendons was negatively correlated; the thickness of the corrugated steel web and the yield strength, and the closest distance from the loading point to the support had little effect on the stress increment of the external prestressed tendons.