Abstract: In order to study the torsional property of a new structure named prestressed composite trough girder with corrugated steel webs, the calculation expression of constrained torsional warping stress and the sectorial inertia moment of a composite trough girder with corrugated steel webs are deduced, based on constrained torsional theory for open thin-walled members. The accordion effect and the shear deformation of corrugated steel webs, which affects the longitudinal rigidity and weakens the constrained torsional stiffness respectively, are taken into account. Then a modified formula for the sectorial inertia moment is proposed, and a torsional angle formula under a concentrated torque is derived. 2 eccentric loading tests and 3 symmetrical loading tests of composite trough girders with corrugated steel webs were conducted. The test results indicate that the loading-displacement curves of test beams are linear when the eccentric loads are less than 90kN. The mean vertical displacements of test beams at the two sides are approximately the same with that of the test beams under symmetrical loading. The eccentric load coefficients of test beams are between 1.2 and 1.3, which are about 10% bigger than that of the box girder with corrugated steel webs. The theoretical calculation, experimental result, and finite element analysis indicate that the proposed torsional angle formula is rational when it used to calculate the re-corrected sectorial inertia moment.