The invention relates to a limiting method for preventing a main tower system of a stayed-cable bridge of a floating system from being damaged by arranging a stay wire below a beam end. The method comprises a traditional elastic stay wire connecting device and a disposal scheme of the device. An elastic stay wire spacing device is arranged between a main beam and the pier top of a bridge pier, wherein the upper end of a stay wire is linked with a main beam in an anchoring manner, and the lower end of the stay wire is linked with the top of the bridge pier or a bridge abutment in an anchoring manner. When a bracket is under the action of an earthquake, the stay wire comes into play and can effectively reduce the earthquake horizontal displacement of the main beam without causing obvious change of earthquake response of the main tower. In conclusion, the scheme that the stay wire is arranged below the beam end for limiting has the advantages of simple and reasonable construction, technological innovation, stable performance, and economy and application and has a favorable development and popularization application prospect.