Effects of different load modes, rise-span ratios and support conditions on out-of-plane buckling and differences between parabolic and circular arches were studied. With the increase of rise-span ratio, buckling loads of arches under vertical load uniformly distributed along the horizontal line get bigger and bigger compared with those of vertical load uniformly distributed along the axis. With increase of rise-span ratio, the buckling loads of hingeless and two-hinged arch increase after decrease, then decrease. The buckling load of three-hinged arch decreases after increases. When rise-span ratio is small, support condition has a great influence on out-of-plane buckling. The parabolic arch is better than circular arch in out-of-plane stability and economy. But circular arch is better than parabolic arch in manufacture.