Combined with the practical design of a prestressed concrete continuous box-girder bridge with changed sections, the effect of side-web slope on the loading properties of this bridge was analyzed. The numerical modes of this bridge were built using the specialist FEM software, 5 side-web slopes were considered by changing the width of box floor. The results show that the changes of side-web slope influence the mid-span deflection of box-girder in a small range under vehicle load, but affect obviously on the transversal loading properties such as crack width and flexural resistance of the box roof. Based on this, the suitable side-web slope is selected. It may be referenced by the similar design of this kind of bridges.