Straight-wall arches have been widely applied in civil engineering. Considering displacements at the arch springing, the arch model was assumed as elastically supported horizontally. Distribution of the bending moments was deduced using classical force method. The distribution and the inflection point of the bending moment were studied under uniformly distributed, triangular and concentrated loads, respectively. Central angle corresponding to zero bending moment at the springing was calculated, which decreased when the load changed from uniformly distributed load, triangular load to concentrated load. Horizontal constraint from the side wall was assumed as elastic support and the equivalent spring stiffness was deduced. With the increase of the straight-wall height, bending moment at the crown increased while that at the springing decreased. When the moment at the springing was zero, anti-flexural capacity at the crown and anti-shearing ability at the springing were improved. Straight-wall height and central angle should be selected to make the moment at the springing zero.