Modern arch bridges are developing in the direction of long span and light weight, while the structural system, layout, and construction method show complexity and diversity. This paper presents a discussion on reasonable arch axis of long-span arch bridges. The development history and thrust line theory were briefly reviewed firstly for arch bridge. Then the dead load distribution and calculation methods of reasonable arch axis were established. Finally, the affact of construction method on reasonable arch axis was determined. Additionally, the future development trend of lightweight and construction technology of long-span arch bridges were prospected. The results show that the arch axis directly affects the stress generated by the loads acting on the arch. The cost of materials and construction, as well as the beauty of arches, are all directly related to the arch axis. As a result, the reasonable arch axis is still needed in the design and construction of long-span arch bridges. The focus of reasonable arch axis calculation is to determine the dead load diestribution on main arch rib and building on the arch bridge.