Abstract：The deformation and failure mechanism of voussoir beam are analyzed by physical modeling test. The relationship curves among deflection，axial load，transverse load，lever arm coefficient of voussior beam are obtained. These curves show the progressive failure process of voussior beam before and after peak. Among the three sets of curves，the curve of deflection vs coefficient of lever arm reaches the peak at first，and then the curves of transverse load and the axial thrust do，which means that the coefficient of lever arm is the most critical to the failure of voussoir beam. The curves are divided into different sections and analyzed. The peak of axial thrust is about twice magnitude of that in the former test due to the direct influences of geometry non-linearity and the test plan.
