Cantilever installation is a construction method of which is often used in the construction of Concrete Oblique-pulling truss bridge. For ensuring the safety of construction process, the structural line shape and stress under different construction phases of the bridge were tested. Contrastive analysis between the testing results and the calculating results was carried on in different construction phases. The results showed the testing values of vertical displacement is smaller than the calculating values because the actual stiffness of the structure is bigger than the theory stiffness. But the stress of key section’s stress of the truss bridge in the whole construction phases agreed pretty well between the testing results and the calculating results. The maximal cantilever length phase to entire bridge closure phase is the most disadvantageous state in the whole construction process.