This paper deals with the assessment of load carrying capacity and safety of PSC-girder bridge decks. It has been observed from the result of load test and analysis that the differential deflection between girders in PSC-girder bridge deck reduces the negative bending moments in the deck slab. In this study, closed-form analysis method considering the effect of girder deflection is developed, based on the elastic plate theory. In this study, analytical solution with the elastic plate theory and numerical analyses with finite element modeling are performed and the results are compared with those of experimental studies for PSC-girder bridge. As a result, the differential deflection of the girders, which can greatly reducethe negative moments in a deck slab, tensile stresses of top slab is reduced. The analytical solution and 3-D shell modeling presented in this paper more accurate in estimating these results.