In order to study the full-range mechanical behavior of prestressed composite box girders with corrugated steel webs subject to pure torsion, a series of equations satisfying the equilibrium, compatibility conditions and constitutive laws of materials were established based on the softened membrane model for torsion(SMMT) and the structural features and the mechanical characteristics of the type of bridge. According to the yielding state or the unyielding state of the corrugated steel web, the continuous shear flow and continuous shear strain conditions in the equations shall be employed to describe the relationship between the steel web and the concrete flanges. Furthermore, the flow chart of solving the equations was given, and thus, the full-range analytical model for prestressed composite box girders with corrugated steel webs subject to pure torsion was proposed. Eight specimens from the literatures were selected for verification of the model. The results show that the entire torque-twist curves, including the ascending stage before cracking of concrete and the descending stage after the limit state, agree well with the experimental curves. In addition, the torque and twist values in both cracking and limit states predicted by the model are close to those from tests, validating the effectiveness and accuracy of the proposed model.